[PATCHv5 00/23] git notes merge

[PATCHv5 00/23] git notes merge

[Johan Herland]

Hi,

This is the 5th iteration of the 'git notes merge' patch series.

In short, patch #5 has an updated commit message, patch #6 has a
minor improvement, patch #16 has renames "--reset" to "--abort",
and there are 2 new patches at the end (totally independent from
the other patches) implementing 'git merge --abort'. Feel free to
consider the two last patches separately from the rest of the series.

Changes between v4 and v5:

- (Jonathan Nieder) Improved commit messages

- (Jonathan Nieder) Improve clarity of final if-condition in
  note_tree_insert()

- (Sverre Rabbelier) Rename 'git notes merge --reset' to
  'git notes merge --abort'.

- Introduce 'git merge --abort' as a synonym of 'git reset --merge'
  (when MERGE_HEAD is present).


Some open questions (not already being discussed in other threads):

- Should we refuse to finalize a notes merge when conflict markers
  present in .git/NOTES_MERGE_WORKTREE? Since add/commit in regular
  merges does NOT do this, I have not implemented it for notes merge.


Have fun! :)

...Johan


Johan Herland (23):
  notes.c: Hexify SHA1 in die() message from init_notes()
  (trivial) notes.h: Minor documentation fixes to copy_notes()
  notes.h: Make default_notes_ref() available in notes API
  notes.c: Reorder functions in preparation for next commit
  notes.h/c: Allow combine_notes functions to remove notes
  notes.h/c: Propagate combine_notes_fn return value to add_note() and beyond
  (trivial) t3303: Indent with tabs instead of spaces for consistency
  notes.c: Use two newlines (instead of one) when concatenating notes
  builtin/notes.c: Split notes ref DWIMmery into a separate function
  git notes merge: Initial implementation handling trivial merges only
  builtin/notes.c: Refactor creation of notes commits.
  git notes merge: Handle real, non-conflicting notes merges
  git notes merge: Add automatic conflict resolvers (ours, theirs, union)
  Documentation: Preliminary docs on 'git notes merge'
  git notes merge: Manual conflict resolution, part 1/2
  git notes merge: Manual conflict resolution, part 2/2
  git notes merge: List conflicting notes in notes merge commit message
  git notes merge: --commit should fail if underlying notes ref has moved
  git notes merge: Add another auto-resolving strategy: "cat_sort_uniq"
  git notes merge: Add testcases for merging notes trees at different fanouts
  Provide 'git notes get-ref' to easily retrieve current notes ref
  cmd_merge(): Parse options before checking MERGE_HEAD
  Provide 'git merge --abort' as a synonym to 'git reset --merge'

 Documentation/git-merge.txt           |   29 ++-
 Documentation/git-notes.txt           |   85 ++++-
 Makefile                              |    2 +
 builtin.h                             |    2 +-
 builtin/merge.c                       |   47 ++-
 builtin/notes.c                       |  268 +++++++++++--
 notes-cache.c                         |    3 +-
 notes-merge.c                         |  735 +++++++++++++++++++++++++++++++++
 notes-merge.h                         |   98 +++++
 notes.c                               |  272 ++++++++----
 notes.h                               |   47 ++-
 t/t3301-notes.sh                      |   23 +
 t/t3303-notes-subtrees.sh             |   19 +-
 t/t3308-notes-merge.sh                |  368 +++++++++++++++++
 t/t3309-notes-merge-auto-resolve.sh   |  647 +++++++++++++++++++++++++++++
 t/t3310-notes-merge-manual-resolve.sh |  556 +++++++++++++++++++++++++
 t/t3311-notes-merge-fanout.sh         |  436 +++++++++++++++++++
 t/t3404-rebase-interactive.sh         |    1 +
 t/t7609-merge-abort.sh                |  273 ++++++++++++
 t/t9301-fast-import-notes.sh          |    5 +
 20 files changed, 3754 insertions(+), 162 deletions(-)
 create mode 100644 notes-merge.c
 create mode 100644 notes-merge.h
 create mode 100755 t/t3308-notes-merge.sh
 create mode 100755 t/t3309-notes-merge-auto-resolve.sh
 create mode 100755 t/t3310-notes-merge-manual-resolve.sh
 create mode 100755 t/t3311-notes-merge-fanout.sh
 create mode 100755 t/t7609-merge-abort.sh

--
1.7.3.98.g5ad7d9

[PATCHv5 01/23] notes.c: Hexify SHA1 in die() message from init_notes()

[Johan Herland]

Signed-off-by: Johan Herland <johan@herland.net>
---
 notes.c |    2 +-
 1 files changed, 1 insertions(+), 1 deletions(-)

diff --git a/notes.c b/notes.c
index 1978244..bb03eb0 100644
--- a/notes.c
+++ b/notes.c
@@ -940,7 +940,7 @@ void init_notes(struct notes_tree *t, const char *notes_ref,
 		return;
 	if (get_tree_entry(object_sha1, "", sha1, &mode))
 		die("Failed to read notes tree referenced by %s (%s)",
-		    notes_ref, object_sha1);
+		    notes_ref, sha1_to_hex(object_sha1));
 
 	hashclr(root_tree.key_sha1);
 	hashcpy(root_tree.val_sha1, sha1);
-- 
1.7.3.98.g5ad7d9

[PATCHv5 02/23] (trivial) notes.h: Minor documentation fixes to copy_notes()

[Johan Herland]

Signed-off-by: Johan Herland <johan@herland.net>
---
 notes.h |    5 +++++
 1 files changed, 5 insertions(+), 0 deletions(-)

diff --git a/notes.h b/notes.h
index 65fc3a6..c0288b0 100644
--- a/notes.h
+++ b/notes.h
@@ -104,6 +104,10 @@ const unsigned char *get_note(struct notes_tree *t,
  * Copy a note from one object to another in the given notes_tree.
  *
  * Fails if the to_obj already has a note unless 'force' is true.
+ *
+ * IMPORTANT: The changes made by copy_note() to the given notes_tree structure
+ * are not persistent until a subsequent call to write_notes_tree() returns
+ * zero.
  */
 int copy_note(struct notes_tree *t,
 	      const unsigned char *from_obj, const unsigned char *to_obj,
@@ -149,6 +153,7 @@ int copy_note(struct notes_tree *t,
  * notes tree) from within the callback:
  * - add_note()
  * - remove_note()
+ * - copy_note()
  * - free_notes()
  */
 typedef int each_note_fn(const unsigned char *object_sha1,
-- 
1.7.3.98.g5ad7d9

[PATCHv5 03/23] notes.h: Make default_notes_ref() available in notes API

[Johan Herland]

Signed-off-by: Johan Herland <johan@herland.net>
---
 notes.c |    2 +-
 notes.h |   14 ++++++++++++++
 2 files changed, 15 insertions(+), 1 deletions(-)

diff --git a/notes.c b/notes.c
index bb03eb0..d71c0a3 100644
--- a/notes.c
+++ b/notes.c
@@ -898,7 +898,7 @@ static int notes_display_config(const char *k, const char *v, void *cb)
 	return 0;
 }
 
-static const char *default_notes_ref(void)
+const char *default_notes_ref(void)
 {
 	const char *notes_ref = NULL;
 	if (!notes_ref)
diff --git a/notes.h b/notes.h
index c0288b0..20db42f 100644
--- a/notes.h
+++ b/notes.h
@@ -44,6 +44,20 @@ extern struct notes_tree {
 } default_notes_tree;
 
 /*
+ * Return the default notes ref.
+ *
+ * The default notes ref is the notes ref that is used when notes_ref == NULL
+ * is passed to init_notes().
+ *
+ * This the first of the following to be defined:
+ * 1. The '--ref' option to 'git notes', if given
+ * 2. The $GIT_NOTES_REF environment variable, if set
+ * 3. The value of the core.notesRef config variable, if set
+ * 4. GIT_NOTES_DEFAULT_REF (i.e. "refs/notes/commits")
+ */
+const char *default_notes_ref(void);
+
+/*
  * Flags controlling behaviour of notes tree initialization
  *
  * Default behaviour is to initialize the notes tree from the tree object
-- 
1.7.3.98.g5ad7d9

[PATCHv5 04/23] notes.c: Reorder functions in preparation for next commit

[Johan Herland]

This patch introduces no functional change. It consists solely of reordering
functions in notes.c to avoid use-before-declaration errors after applying
the next commit in this series.

Signed-off-by: Johan Herland <johan@herland.net>
---
 notes.c |  146 +++++++++++++++++++++++++++++++-------------------------------
 1 files changed, 73 insertions(+), 73 deletions(-)

diff --git a/notes.c b/notes.c
index d71c0a3..bfb3ea5 100644
--- a/notes.c
+++ b/notes.c
@@ -150,6 +150,79 @@ static struct leaf_node *note_tree_find(struct notes_tree *t,
 }
 
 /*
+ * How to consolidate an int_node:
+ * If there are > 1 non-NULL entries, give up and return non-zero.
+ * Otherwise replace the int_node at the given index in the given parent node
+ * with the only entry (or a NULL entry if no entries) from the given tree,
+ * and return 0.
+ */
+static int note_tree_consolidate(struct int_node *tree,
+	struct int_node *parent, unsigned char index)
+{
+	unsigned int i;
+	void *p = NULL;
+
+	assert(tree && parent);
+	assert(CLR_PTR_TYPE(parent->a[index]) == tree);
+
+	for (i = 0; i < 16; i++) {
+		if (GET_PTR_TYPE(tree->a[i]) != PTR_TYPE_NULL) {
+			if (p) /* more than one entry */
+				return -2;
+			p = tree->a[i];
+		}
+	}
+
+	/* replace tree with p in parent[index] */
+	parent->a[index] = p;
+	free(tree);
+	return 0;
+}
+
+/*
+ * To remove a leaf_node:
+ * Search to the tree location appropriate for the given leaf_node's key:
+ * - If location does not hold a matching entry, abort and do nothing.
+ * - Replace the matching leaf_node with a NULL entry (and free the leaf_node).
+ * - Consolidate int_nodes repeatedly, while walking up the tree towards root.
+ */
+static void note_tree_remove(struct notes_tree *t, struct int_node *tree,
+		unsigned char n, struct leaf_node *entry)
+{
+	struct leaf_node *l;
+	struct int_node *parent_stack[20];
+	unsigned char i, j;
+	void **p = note_tree_search(t, &tree, &n, entry->key_sha1);
+
+	assert(GET_PTR_TYPE(entry) == 0); /* no type bits set */
+	if (GET_PTR_TYPE(*p) != PTR_TYPE_NOTE)
+		return; /* type mismatch, nothing to remove */
+	l = (struct leaf_node *) CLR_PTR_TYPE(*p);
+	if (hashcmp(l->key_sha1, entry->key_sha1))
+		return; /* key mismatch, nothing to remove */
+
+	/* we have found a matching entry */
+	free(l);
+	*p = SET_PTR_TYPE(NULL, PTR_TYPE_NULL);
+
+	/* consolidate this tree level, and parent levels, if possible */
+	if (!n)
+		return; /* cannot consolidate top level */
+	/* first, build stack of ancestors between root and current node */
+	parent_stack[0] = t->root;
+	for (i = 0; i < n; i++) {
+		j = GET_NIBBLE(i, entry->key_sha1);
+		parent_stack[i + 1] = CLR_PTR_TYPE(parent_stack[i]->a[j]);
+	}
+	assert(i == n && parent_stack[i] == tree);
+	/* next, unwind stack until note_tree_consolidate() is done */
+	while (i > 0 &&
+	       !note_tree_consolidate(parent_stack[i], parent_stack[i - 1],
+				      GET_NIBBLE(i - 1, entry->key_sha1)))
+		i--;
+}
+
+/*
  * To insert a leaf_node:
  * Search to the tree location appropriate for the given leaf_node's key:
  * - If location is unused (NULL), store the tweaked pointer directly there
@@ -229,79 +302,6 @@ static void note_tree_insert(struct notes_tree *t, struct int_node *tree,
 	note_tree_insert(t, new_node, n + 1, entry, type, combine_notes);
 }
 
-/*
- * How to consolidate an int_node:
- * If there are > 1 non-NULL entries, give up and return non-zero.
- * Otherwise replace the int_node at the given index in the given parent node
- * with the only entry (or a NULL entry if no entries) from the given tree,
- * and return 0.
- */
-static int note_tree_consolidate(struct int_node *tree,
-	struct int_node *parent, unsigned char index)
-{
-	unsigned int i;
-	void *p = NULL;
-
-	assert(tree && parent);
-	assert(CLR_PTR_TYPE(parent->a[index]) == tree);
-
-	for (i = 0; i < 16; i++) {
-		if (GET_PTR_TYPE(tree->a[i]) != PTR_TYPE_NULL) {
-			if (p) /* more than one entry */
-				return -2;
-			p = tree->a[i];
-		}
-	}
-
-	/* replace tree with p in parent[index] */
-	parent->a[index] = p;
-	free(tree);
-	return 0;
-}
-
-/*
- * To remove a leaf_node:
- * Search to the tree location appropriate for the given leaf_node's key:
- * - If location does not hold a matching entry, abort and do nothing.
- * - Replace the matching leaf_node with a NULL entry (and free the leaf_node).
- * - Consolidate int_nodes repeatedly, while walking up the tree towards root.
- */
-static void note_tree_remove(struct notes_tree *t, struct int_node *tree,
-		unsigned char n, struct leaf_node *entry)
-{
-	struct leaf_node *l;
-	struct int_node *parent_stack[20];
-	unsigned char i, j;
-	void **p = note_tree_search(t, &tree, &n, entry->key_sha1);
-
-	assert(GET_PTR_TYPE(entry) == 0); /* no type bits set */
-	if (GET_PTR_TYPE(*p) != PTR_TYPE_NOTE)
-		return; /* type mismatch, nothing to remove */
-	l = (struct leaf_node *) CLR_PTR_TYPE(*p);
-	if (hashcmp(l->key_sha1, entry->key_sha1))
-		return; /* key mismatch, nothing to remove */
-
-	/* we have found a matching entry */
-	free(l);
-	*p = SET_PTR_TYPE(NULL, PTR_TYPE_NULL);
-
-	/* consolidate this tree level, and parent levels, if possible */
-	if (!n)
-		return; /* cannot consolidate top level */
-	/* first, build stack of ancestors between root and current node */
-	parent_stack[0] = t->root;
-	for (i = 0; i < n; i++) {
-		j = GET_NIBBLE(i, entry->key_sha1);
-		parent_stack[i + 1] = CLR_PTR_TYPE(parent_stack[i]->a[j]);
-	}
-	assert(i == n && parent_stack[i] == tree);
-	/* next, unwind stack until note_tree_consolidate() is done */
-	while (i > 0 &&
-	       !note_tree_consolidate(parent_stack[i], parent_stack[i - 1],
-				      GET_NIBBLE(i - 1, entry->key_sha1)))
-		i--;
-}
-
 /* Free the entire notes data contained in the given tree */
 static void note_tree_free(struct int_node *tree)
 {
-- 
1.7.3.98.g5ad7d9

[PATCHv5 05/23] notes.h/c: Allow combine_notes functions to remove notes

[Johan Herland]

Allow combine_notes functions to request that a note be removed, by setting
the resulting note SHA1 to null_sha1 (0000000...).

For consistency, also teach note_tree_insert() to skip insertion of an empty
note (a note with entry->val_sha1 equal to null_sha1) when there is no note
to combine it with.

In general, an empty note (null_sha1) is treated identically to no note at
all, but when adding an empty note where there already exists a non-empty
note, we allow the combine_notes function to potentially record a new/changed
note. Document this behaviour, and clearly specify how combine_notes functions
are expected to handle null_sha1 in input.

Before this patch, storing null_sha1s in the notes tree were silently allowed,
causing an invalid notes tree (referring to blobs with null_sha1) to be
produced by write_notes_tree().

Signed-off-by: Johan Herland <johan@herland.net>
---
 notes.c |   12 +++++++++++-
 notes.h |   16 +++++++++++++++-
 2 files changed, 26 insertions(+), 2 deletions(-)

diff --git a/notes.c b/notes.c
index bfb3ea5..0c13a36 100644
--- a/notes.c
+++ b/notes.c
@@ -248,7 +248,10 @@ static void note_tree_insert(struct notes_tree *t, struct int_node *tree,
 	switch (GET_PTR_TYPE(*p)) {
 	case PTR_TYPE_NULL:
 		assert(!*p);
-		*p = SET_PTR_TYPE(entry, type);
+		if (is_null_sha1(entry->val_sha1))
+			free(entry);
+		else
+			*p = SET_PTR_TYPE(entry, type);
 		return;
 	case PTR_TYPE_NOTE:
 		switch (type) {
@@ -264,6 +267,9 @@ static void note_tree_insert(struct notes_tree *t, struct int_node *tree,
 					    sha1_to_hex(l->val_sha1),
 					    sha1_to_hex(entry->val_sha1),
 					    sha1_to_hex(l->key_sha1));
+
+				if (is_null_sha1(l->val_sha1))
+					note_tree_remove(t, tree, n, entry);
 				free(entry);
 				return;
 			}
@@ -295,6 +301,10 @@ static void note_tree_insert(struct notes_tree *t, struct int_node *tree,
 	/* non-matching leaf_node */
 	assert(GET_PTR_TYPE(*p) == PTR_TYPE_NOTE ||
 	       GET_PTR_TYPE(*p) == PTR_TYPE_SUBTREE);
+	if (is_null_sha1(entry->val_sha1)) { /* skip insertion of empty note */
+		free(entry);
+		return;
+	}
 	new_node = (struct int_node *) xcalloc(sizeof(struct int_node), 1);
 	note_tree_insert(t, new_node, n + 1, l, GET_PTR_TYPE(*p),
 			 combine_notes);
diff --git a/notes.h b/notes.h
index 20db42f..79ea797 100644
--- a/notes.h
+++ b/notes.h
@@ -12,7 +12,10 @@
  * resulting SHA1 into the first SHA1 argument (cur_sha1). A non-zero return
  * value indicates failure.
  *
- * The two given SHA1s must both be non-NULL and different from each other.
+ * The two given SHA1s shall both be non-NULL and different from each other.
+ * Either of them (but not both) may be == null_sha1, which indicates an
+ * empty/non-existent note. If the resulting SHA1 (cur_sha1) is == null_sha1,
+ * the note will be removed from the notes tree.
  *
  * The default combine_notes function (you get this when passing NULL) is
  * combine_notes_concatenate(), which appends the contents of the new note to
@@ -90,6 +93,17 @@ void init_notes(struct notes_tree *t, const char *notes_ref,
 /*
  * Add the given note object to the given notes_tree structure
  *
+ * If there already exists a note for the given object_sha1, the given
+ * combine_notes function is invoked to break the tie. If not given (i.e.
+ * combine_notes == NULL), the default combine_notes function for the given
+ * notes_tree is used.
+ *
+ * Passing note_sha1 == null_sha1 indicates the addition of an
+ * empty/non-existent note. This is a (potentially expensive) no-op unless
+ * there already exists a note for the given object_sha1, AND combining that
+ * note with the empty note (using the given combine_notes function) results
+ * in a new/changed note.
+ *
  * IMPORTANT: The changes made by add_note() to the given notes_tree structure
  * are not persistent until a subsequent call to write_notes_tree() returns
  * zero.
-- 
1.7.3.98.g5ad7d9

[PATCHv5 06/23] notes.h/c: Propagate combine_notes_fn return value to add_note() and beyond

[Johan Herland]

The combine_notes_fn functions uses a non-zero return value to indicate
failure. However, this return value was converted to a call to die()
in note_tree_insert().

Instead, propagate this return value out to add_note(), and return it
from there to enable the caller to handle errors appropriately.

Existing add_note() callers are updated to die() upon failure, thus
preserving the current behaviour. The only exceptions are copy_note()
and notes_cache_put() where we are able to propagate the add_note()
return value instead.

This patch has been improved by the following contributions:
- Jonathan Nieder: Future-proof by always checking add_note() return value
- Jonathan Nieder: Improve clarity of final if-condition in note_tree_insert()

Thanks-to: Jonathan Nieder <jrnieder@gmail.com>
Signed-off-by: Johan Herland <johan@herland.net>
---
 builtin/notes.c |   11 ++++++-----
 notes-cache.c   |    3 +--
 notes.c         |   55 ++++++++++++++++++++++++++++---------------------------
 notes.h         |   11 ++++++++---
 4 files changed, 43 insertions(+), 37 deletions(-)

diff --git a/builtin/notes.c b/builtin/notes.c
index fbc347c..35f6eb6 100644
--- a/builtin/notes.c
+++ b/builtin/notes.c
@@ -573,8 +573,8 @@ static int add(int argc, const char **argv, const char *prefix)
 
 	if (is_null_sha1(new_note))
 		remove_note(t, object);
-	else
-		add_note(t, object, new_note, combine_notes_overwrite);
+	else if (add_note(t, object, new_note, combine_notes_overwrite))
+		die("confused: combine_notes_overwrite failed");
 
 	snprintf(logmsg, sizeof(logmsg), "Notes %s by 'git notes %s'",
 		 is_null_sha1(new_note) ? "removed" : "added", "add");
@@ -653,7 +653,8 @@ static int copy(int argc, const char **argv, const char *prefix)
 		goto out;
 	}
 
-	add_note(t, object, from_note, combine_notes_overwrite);
+	if (add_note(t, object, from_note, combine_notes_overwrite))
+		die("confused: combine_notes_overwrite failed");
 	commit_notes(t, "Notes added by 'git notes copy'");
 out:
 	free_notes(t);
@@ -712,8 +713,8 @@ static int append_edit(int argc, const char **argv, const char *prefix)
 
 	if (is_null_sha1(new_note))
 		remove_note(t, object);
-	else
-		add_note(t, object, new_note, combine_notes_overwrite);
+	else if (add_note(t, object, new_note, combine_notes_overwrite))
+		die("confused: combine_notes_overwrite failed");
 
 	snprintf(logmsg, sizeof(logmsg), "Notes %s by 'git notes %s'",
 		 is_null_sha1(new_note) ? "removed" : "added", argv[0]);
diff --git a/notes-cache.c b/notes-cache.c
index dee6d62..4c8984e 100644
--- a/notes-cache.c
+++ b/notes-cache.c
@@ -89,6 +89,5 @@ int notes_cache_put(struct notes_cache *c, unsigned char key_sha1[20],
 
 	if (write_sha1_file(data, size, "blob", value_sha1) < 0)
 		return -1;
-	add_note(&c->tree, key_sha1, value_sha1, NULL);
-	return 0;
+	return add_note(&c->tree, key_sha1, value_sha1, NULL);
 }
diff --git a/notes.c b/notes.c
index 0c13a36..1674391 100644
--- a/notes.c
+++ b/notes.c
@@ -235,13 +235,14 @@ static void note_tree_remove(struct notes_tree *t, struct int_node *tree,
  * - Else, create a new int_node, holding both the node-at-location and the
  *   node-to-be-inserted, and store the new int_node into the location.
  */
-static void note_tree_insert(struct notes_tree *t, struct int_node *tree,
+static int note_tree_insert(struct notes_tree *t, struct int_node *tree,
 		unsigned char n, struct leaf_node *entry, unsigned char type,
 		combine_notes_fn combine_notes)
 {
 	struct int_node *new_node;
 	struct leaf_node *l;
 	void **p = note_tree_search(t, &tree, &n, entry->key_sha1);
+	int ret = 0;
 
 	assert(GET_PTR_TYPE(entry) == 0); /* no type bits set */
 	l = (struct leaf_node *) CLR_PTR_TYPE(*p);
@@ -252,26 +253,21 @@ static void note_tree_insert(struct notes_tree *t, struct int_node *tree,
 			free(entry);
 		else
 			*p = SET_PTR_TYPE(entry, type);
-		return;
+		return 0;
 	case PTR_TYPE_NOTE:
 		switch (type) {
 		case PTR_TYPE_NOTE:
 			if (!hashcmp(l->key_sha1, entry->key_sha1)) {
 				/* skip concatenation if l == entry */
 				if (!hashcmp(l->val_sha1, entry->val_sha1))
-					return;
+					return 0;
 
-				if (combine_notes(l->val_sha1, entry->val_sha1))
-					die("failed to combine notes %s and %s"
-					    " for object %s",
-					    sha1_to_hex(l->val_sha1),
-					    sha1_to_hex(entry->val_sha1),
-					    sha1_to_hex(l->key_sha1));
-
-				if (is_null_sha1(l->val_sha1))
+				ret = combine_notes(l->val_sha1,
+						    entry->val_sha1);
+				if (!ret && is_null_sha1(l->val_sha1))
 					note_tree_remove(t, tree, n, entry);
 				free(entry);
-				return;
+				return ret;
 			}
 			break;
 		case PTR_TYPE_SUBTREE:
@@ -280,7 +276,7 @@ static void note_tree_insert(struct notes_tree *t, struct int_node *tree,
 				/* unpack 'entry' */
 				load_subtree(t, entry, tree, n);
 				free(entry);
-				return;
+				return 0;
 			}
 			break;
 		}
@@ -291,9 +287,8 @@ static void note_tree_insert(struct notes_tree *t, struct int_node *tree,
 			*p = NULL;
 			load_subtree(t, l, tree, n);
 			free(l);
-			note_tree_insert(t, tree, n, entry, type,
-					 combine_notes);
-			return;
+			return note_tree_insert(t, tree, n, entry, type,
+						combine_notes);
 		}
 		break;
 	}
@@ -303,13 +298,15 @@ static void note_tree_insert(struct notes_tree *t, struct int_node *tree,
 	       GET_PTR_TYPE(*p) == PTR_TYPE_SUBTREE);
 	if (is_null_sha1(entry->val_sha1)) { /* skip insertion of empty note */
 		free(entry);
-		return;
+		return 0;
 	}
 	new_node = (struct int_node *) xcalloc(sizeof(struct int_node), 1);
-	note_tree_insert(t, new_node, n + 1, l, GET_PTR_TYPE(*p),
-			 combine_notes);
+	ret = note_tree_insert(t, new_node, n + 1, l, GET_PTR_TYPE(*p),
+			       combine_notes);
+	if (ret)
+		return ret;
 	*p = SET_PTR_TYPE(new_node, PTR_TYPE_INTERNAL);
-	note_tree_insert(t, new_node, n + 1, entry, type, combine_notes);
+	return note_tree_insert(t, new_node, n + 1, entry, type, combine_notes);
 }
 
 /* Free the entire notes data contained in the given tree */
@@ -452,8 +449,12 @@ static void load_subtree(struct notes_tree *t, struct leaf_node *subtree,
 				l->key_sha1[19] = (unsigned char) len;
 				type = PTR_TYPE_SUBTREE;
 			}
-			note_tree_insert(t, node, n, l, type,
-					 combine_notes_concatenate);
+			if (note_tree_insert(t, node, n, l, type,
+					     combine_notes_concatenate))
+				die("Failed to load %s %s into notes tree "
+				    "from %s",
+				    type == PTR_TYPE_NOTE ? "note" : "subtree",
+				    sha1_to_hex(l->key_sha1), t->ref);
 		}
 		continue;
 
@@ -1014,7 +1015,7 @@ void init_display_notes(struct display_notes_opt *opt)
 	string_list_clear(&display_notes_refs, 0);
 }
 
-void add_note(struct notes_tree *t, const unsigned char *object_sha1,
+int add_note(struct notes_tree *t, const unsigned char *object_sha1,
 		const unsigned char *note_sha1, combine_notes_fn combine_notes)
 {
 	struct leaf_node *l;
@@ -1028,7 +1029,7 @@ void add_note(struct notes_tree *t, const unsigned char *object_sha1,
 	l = (struct leaf_node *) xmalloc(sizeof(struct leaf_node));
 	hashcpy(l->key_sha1, object_sha1);
 	hashcpy(l->val_sha1, note_sha1);
-	note_tree_insert(t, t->root, 0, l, PTR_TYPE_NOTE, combine_notes);
+	return note_tree_insert(t, t->root, 0, l, PTR_TYPE_NOTE, combine_notes);
 }
 
 void remove_note(struct notes_tree *t, const unsigned char *object_sha1)
@@ -1204,7 +1205,7 @@ void format_display_notes(const unsigned char *object_sha1,
 
 int copy_note(struct notes_tree *t,
 	      const unsigned char *from_obj, const unsigned char *to_obj,
-	      int force, combine_notes_fn combine_fn)
+	      int force, combine_notes_fn combine_notes)
 {
 	const unsigned char *note = get_note(t, from_obj);
 	const unsigned char *existing_note = get_note(t, to_obj);
@@ -1213,9 +1214,9 @@ int copy_note(struct notes_tree *t,
 		return 1;
 
 	if (note)
-		add_note(t, to_obj, note, combine_fn);
+		return add_note(t, to_obj, note, combine_notes);
 	else if (existing_note)
-		add_note(t, to_obj, null_sha1, combine_fn);
+		return add_note(t, to_obj, null_sha1, combine_notes);
 
 	return 0;
 }
diff --git a/notes.h b/notes.h
index 79ea797..b372575 100644
--- a/notes.h
+++ b/notes.h
@@ -104,11 +104,13 @@ void init_notes(struct notes_tree *t, const char *notes_ref,
  * note with the empty note (using the given combine_notes function) results
  * in a new/changed note.
  *
+ * Returns zero on success; non-zero means combine_notes failed.
+ *
  * IMPORTANT: The changes made by add_note() to the given notes_tree structure
  * are not persistent until a subsequent call to write_notes_tree() returns
  * zero.
  */
-void add_note(struct notes_tree *t, const unsigned char *object_sha1,
+int add_note(struct notes_tree *t, const unsigned char *object_sha1,
 		const unsigned char *note_sha1, combine_notes_fn combine_notes);
 
 /*
@@ -131,7 +133,10 @@ const unsigned char *get_note(struct notes_tree *t,
 /*
  * Copy a note from one object to another in the given notes_tree.
  *
- * Fails if the to_obj already has a note unless 'force' is true.
+ * Returns 1 if the to_obj already has a note and 'force' is false. Otherwise,
+ * returns non-zero if 'force' is true, but the given combine_notes function
+ * failed to combine from_obj's note with to_obj's existing note.
+ * Returns zero on success.
  *
  * IMPORTANT: The changes made by copy_note() to the given notes_tree structure
  * are not persistent until a subsequent call to write_notes_tree() returns
@@ -139,7 +144,7 @@ const unsigned char *get_note(struct notes_tree *t,
  */
 int copy_note(struct notes_tree *t,
 	      const unsigned char *from_obj, const unsigned char *to_obj,
-	      int force, combine_notes_fn combine_fn);
+	      int force, combine_notes_fn combine_notes);
 
 /*
  * Flags controlling behaviour of for_each_note()
-- 
1.7.3.98.g5ad7d9

[PATCHv5 07/23] (trivial) t3303: Indent with tabs instead of spaces for consistency

[Johan Herland]

The rest of the file uses tabs for indenting. Fix the one function
that doesn't.

Signed-off-by: Johan Herland <johan@herland.net>
---
 t/t3303-notes-subtrees.sh |   18 +++++++++---------
 1 files changed, 9 insertions(+), 9 deletions(-)

diff --git a/t/t3303-notes-subtrees.sh b/t/t3303-notes-subtrees.sh
index 75ec187..d571708 100755
--- a/t/t3303-notes-subtrees.sh
+++ b/t/t3303-notes-subtrees.sh
@@ -168,15 +168,15 @@ INPUT_END
 }
 
 verify_concatenated_notes () {
-    git log | grep "^    " > output &&
-    i=$number_of_commits &&
-    while [ $i -gt 0 ]; do
-        echo "    commit #$i" &&
-        echo "    first note for commit #$i" &&
-        echo "    second note for commit #$i" &&
-        i=$(($i-1));
-    done > expect &&
-    test_cmp expect output
+	git log | grep "^    " > output &&
+	i=$number_of_commits &&
+	while [ $i -gt 0 ]; do
+		echo "    commit #$i" &&
+		echo "    first note for commit #$i" &&
+		echo "    second note for commit #$i" &&
+		i=$(($i-1));
+	done > expect &&
+	test_cmp expect output
 }
 
 test_expect_success 'test notes in no fanout concatenated with 2/38-fanout' 'test_concatenated_notes "s|^..|&/|" ""'
-- 
1.7.3.98.g5ad7d9

[PATCHv5 08/23] notes.c: Use two newlines (instead of one) when concatenating notes

[Johan Herland]

When using combine_notes_concatenate() to concatenate notes, it currently
ensures exactly one newline character between the given notes. However,
when using builtin/notes.c:create_note() to concatenate notes (e.g. by
'git notes append'), it adds a newline character to the trailing newline
of the preceding notes object, thus resulting in _two_ newlines (aka. a
blank line) separating contents of the two notes.

This patch brings combine_notes_concatenate() into consistency with
builtin/notes.c:create_note(), by ensuring exactly _two_ newline characters
between concatenated notes.

The patch also changes a few notes-related selftests accordingly.

Signed-off-by: Johan Herland <johan@herland.net>
---
 notes.c                       |    7 ++++---
 t/t3301-notes.sh              |    4 ++++
 t/t3303-notes-subtrees.sh     |    1 +
 t/t3404-rebase-interactive.sh |    1 +
 t/t9301-fast-import-notes.sh  |    5 +++++
 5 files changed, 15 insertions(+), 3 deletions(-)

diff --git a/notes.c b/notes.c
index 1674391..09a93ab 100644
--- a/notes.c
+++ b/notes.c
@@ -812,16 +812,17 @@ int combine_notes_concatenate(unsigned char *cur_sha1,
 		return 0;
 	}
 
-	/* we will separate the notes by a newline anyway */
+	/* we will separate the notes by two newlines anyway */
 	if (cur_msg[cur_len - 1] == '\n')
 		cur_len--;
 
 	/* concatenate cur_msg and new_msg into buf */
-	buf_len = cur_len + 1 + new_len;
+	buf_len = cur_len + 2 + new_len;
 	buf = (char *) xmalloc(buf_len);
 	memcpy(buf, cur_msg, cur_len);
 	buf[cur_len] = '\n';
-	memcpy(buf + cur_len + 1, new_msg, new_len);
+	buf[cur_len + 1] = '\n';
+	memcpy(buf + cur_len + 2, new_msg, new_len);
 	free(cur_msg);
 	free(new_msg);
 
diff --git a/t/t3301-notes.sh b/t/t3301-notes.sh
index 1d82f79..4bf4e52 100755
--- a/t/t3301-notes.sh
+++ b/t/t3301-notes.sh
@@ -955,6 +955,7 @@ Date:   Thu Apr 7 15:27:13 2005 -0700
 
 Notes (other):
     a fresh note
+$whitespace
     another fresh note
 EOF
 
@@ -976,8 +977,11 @@ Date:   Thu Apr 7 15:27:13 2005 -0700
 
 Notes (other):
     a fresh note
+$whitespace
     another fresh note
+$whitespace
     append 1
+$whitespace
     append 2
 EOF
 
diff --git a/t/t3303-notes-subtrees.sh b/t/t3303-notes-subtrees.sh
index d571708..704aee8 100755
--- a/t/t3303-notes-subtrees.sh
+++ b/t/t3303-notes-subtrees.sh
@@ -173,6 +173,7 @@ verify_concatenated_notes () {
 	while [ $i -gt 0 ]; do
 		echo "    commit #$i" &&
 		echo "    first note for commit #$i" &&
+		echo "    " &&
 		echo "    second note for commit #$i" &&
 		i=$(($i-1));
 	done > expect &&
diff --git a/t/t3404-rebase-interactive.sh b/t/t3404-rebase-interactive.sh
index 9f03ce6..9ed70dc 100755
--- a/t/t3404-rebase-interactive.sh
+++ b/t/t3404-rebase-interactive.sh
@@ -593,6 +593,7 @@ test_expect_success 'rebase -i can copy notes' '
 
 cat >expect <<EOF
 an earlier note
+
 a note
 EOF
 
diff --git a/t/t9301-fast-import-notes.sh b/t/t9301-fast-import-notes.sh
index a5c99d8..7cf8cd8 100755
--- a/t/t9301-fast-import-notes.sh
+++ b/t/t9301-fast-import-notes.sh
@@ -255,13 +255,18 @@ EOF
 
 INPUT_END
 
+whitespace="    "
+
 cat >expect <<EXPECT_END
     fourth commit
     pre-prefix of note for fourth commit
+$whitespace
     prefix of note for fourth commit
+$whitespace
     third note for fourth commit
     third commit
     prefix of note for third commit
+$whitespace
     third note for third commit
     second commit
     third note for second commit
-- 
1.7.3.98.g5ad7d9

[PATCHv5 09/23] builtin/notes.c: Split notes ref DWIMmery into a separate function

[Johan Herland]

expand_notes_ref() is a new function that performs the DWIM transformation
of "foo" -> "refs/notes/foo" where notes refs are expected.

This is done in preparation for future patches which will also need this
DWIM functionality.

Signed-off-by: Johan Herland <johan@herland.net>
---
 builtin/notes.c |   17 +++++++++++------
 1 files changed, 11 insertions(+), 6 deletions(-)

diff --git a/builtin/notes.c b/builtin/notes.c
index 35f6eb6..9c91c59 100644
--- a/builtin/notes.c
+++ b/builtin/notes.c
@@ -83,6 +83,16 @@ struct msg_arg {
 	struct strbuf buf;
 };
 
+static void expand_notes_ref(struct strbuf *sb)
+{
+	if (!prefixcmp(sb->buf, "refs/notes/"))
+		return; /* we're happy */
+	else if (!prefixcmp(sb->buf, "notes/"))
+		strbuf_insert(sb, 0, "refs/", 5);
+	else
+		strbuf_insert(sb, 0, "refs/notes/", 11);
+}
+
 static int list_each_note(const unsigned char *object_sha1,
 		const unsigned char *note_sha1, char *note_path,
 		void *cb_data)
@@ -839,13 +849,8 @@ int cmd_notes(int argc, const char **argv, const char *prefix)
 
 	if (override_notes_ref) {
 		struct strbuf sb = STRBUF_INIT;
-		if (!prefixcmp(override_notes_ref, "refs/notes/"))
-			/* we're happy */;
-		else if (!prefixcmp(override_notes_ref, "notes/"))
-			strbuf_addstr(&sb, "refs/");
-		else
-			strbuf_addstr(&sb, "refs/notes/");
 		strbuf_addstr(&sb, override_notes_ref);
+		expand_notes_ref(&sb);
 		setenv("GIT_NOTES_REF", sb.buf, 1);
 		strbuf_release(&sb);
 	}
-- 
1.7.3.98.g5ad7d9

[PATCHv5 10/23] git notes merge: Initial implementation handling trivial merges only

[Johan Herland]

This initial implementation of 'git notes merge' only handles the trivial
merge cases (i.e. where the merge is either a no-op, or a fast-forward).

The patch includes testcases for these trivial merge cases.

Future patches will extend the functionality of 'git notes merge'.

This patch has been improved by the following contributions:
- Stephen Boyd: Simplify argc logic
- Stephen Boyd: Use test_commit
- Ævar Arnfjörð Bjarmason: Don't use C99 comments.
- Jonathan Nieder: Add constants for common verbosity values
- Jonathan Nieder: Use trace_printf(...) instead of OUTPUT(o, 5, ...)
- Jonathan Nieder: Remove extraneous show() function
- Jonathan Nieder: Clarify handling of empty/missing notes ref in notes_merge()

Thanks-to: Stephen Boyd <bebarino@gmail.com>
Thanks-to: Ævar Arnfjörð Bjarmason <avarab@gmail.com>
Thanks-to: Jonathan Nieder <jrnieder@gmail.com>
Signed-off-by: Johan Herland <johan@herland.net>
---
 Makefile               |    2 +
 builtin/notes.c        |   54 ++++++++++++++
 notes-merge.c          |  120 ++++++++++++++++++++++++++++++++
 notes-merge.h          |   36 ++++++++++
 t/t3308-notes-merge.sh |  180 ++++++++++++++++++++++++++++++++++++++++++++++++
 5 files changed, 392 insertions(+), 0 deletions(-)
 create mode 100644 notes-merge.c
 create mode 100644 notes-merge.h
 create mode 100755 t/t3308-notes-merge.sh

diff --git a/Makefile b/Makefile
index f33648d..14c0ff1 100644
--- a/Makefile
+++ b/Makefile
@@ -503,6 +503,7 @@ LIB_H += mailmap.h
 LIB_H += merge-recursive.h
 LIB_H += notes.h
 LIB_H += notes-cache.h
+LIB_H += notes-merge.h
 LIB_H += object.h
 LIB_H += pack.h
 LIB_H += pack-refs.h
@@ -593,6 +594,7 @@ LIB_OBJS += merge-recursive.o
 LIB_OBJS += name-hash.o
 LIB_OBJS += notes.o
 LIB_OBJS += notes-cache.o
+LIB_OBJS += notes-merge.o
 LIB_OBJS += object.o
 LIB_OBJS += pack-check.o
 LIB_OBJS += pack-refs.o
diff --git a/builtin/notes.c b/builtin/notes.c
index 9c91c59..fbabdc7 100644
--- a/builtin/notes.c
+++ b/builtin/notes.c
@@ -17,6 +17,7 @@
 #include "run-command.h"
 #include "parse-options.h"
 #include "string-list.h"
+#include "notes-merge.h"
 
 static const char * const git_notes_usage[] = {
 	"git notes [--ref <notes_ref>] [list [<object>]]",
@@ -25,6 +26,7 @@ static const char * const git_notes_usage[] = {
 	"git notes [--ref <notes_ref>] append [-m <msg> | -F <file> | (-c | -C) <object>] [<object>]",
 	"git notes [--ref <notes_ref>] edit [<object>]",
 	"git notes [--ref <notes_ref>] show [<object>]",
+	"git notes [--ref <notes_ref>] merge [-v | -q] <notes_ref>",
 	"git notes [--ref <notes_ref>] remove [<object>]",
 	"git notes [--ref <notes_ref>] prune [-n | -v]",
 	NULL
@@ -61,6 +63,11 @@ static const char * const git_notes_show_usage[] = {
 	NULL
 };
 
+static const char * const git_notes_merge_usage[] = {
+	"git notes merge [<options>] <notes_ref>",
+	NULL
+};
+
 static const char * const git_notes_remove_usage[] = {
 	"git notes remove [<object>]",
 	NULL
@@ -772,6 +779,51 @@ static int show(int argc, const char **argv, const char *prefix)
 	return retval;
 }
 
+static int merge(int argc, const char **argv, const char *prefix)
+{
+	struct strbuf remote_ref = STRBUF_INIT, msg = STRBUF_INIT;
+	unsigned char result_sha1[20];
+	struct notes_merge_options o;
+	int verbosity = 0, result;
+	struct option options[] = {
+		OPT__VERBOSITY(&verbosity),
+		OPT_END()
+	};
+
+	argc = parse_options(argc, argv, prefix, options,
+			     git_notes_merge_usage, 0);
+
+	if (argc != 1) {
+		error("Must specify a notes ref to merge");
+		usage_with_options(git_notes_merge_usage, options);
+	}
+
+	init_notes_merge_options(&o);
+	o.verbosity = verbosity + NOTES_MERGE_VERBOSITY_DEFAULT;
+
+	o.local_ref = default_notes_ref();
+	strbuf_addstr(&remote_ref, argv[0]);
+	expand_notes_ref(&remote_ref);
+	o.remote_ref = remote_ref.buf;
+
+	result = notes_merge(&o, result_sha1);
+
+	strbuf_addf(&msg, "notes: Merged notes from %s into %s",
+		    remote_ref.buf, default_notes_ref());
+	if (result == 0) { /* Merge resulted (trivially) in result_sha1 */
+		/* Update default notes ref with new commit */
+		update_ref(msg.buf, default_notes_ref(), result_sha1, NULL,
+			   0, DIE_ON_ERR);
+	} else {
+		/* TODO: */
+		die("'git notes merge' cannot yet handle non-trivial merges!");
+	}
+
+	strbuf_release(&remote_ref);
+	strbuf_release(&msg);
+	return 0;
+}
+
 static int remove_cmd(int argc, const char **argv, const char *prefix)
 {
 	struct option options[] = {
@@ -865,6 +917,8 @@ int cmd_notes(int argc, const char **argv, const char *prefix)
 		result = append_edit(argc, argv, prefix);
 	else if (!strcmp(argv[0], "show"))
 		result = show(argc, argv, prefix);
+	else if (!strcmp(argv[0], "merge"))
+		result = merge(argc, argv, prefix);
 	else if (!strcmp(argv[0], "remove"))
 		result = remove_cmd(argc, argv, prefix);
 	else if (!strcmp(argv[0], "prune"))
diff --git a/notes-merge.c b/notes-merge.c
new file mode 100644
index 0000000..cd917f9
--- /dev/null
+++ b/notes-merge.c
@@ -0,0 +1,120 @@
+#include "cache.h"
+#include "commit.h"
+#include "refs.h"
+#include "notes-merge.h"
+
+void init_notes_merge_options(struct notes_merge_options *o)
+{
+	memset(o, 0, sizeof(struct notes_merge_options));
+	o->verbosity = NOTES_MERGE_VERBOSITY_DEFAULT;
+}
+
+#define OUTPUT(o, v, ...) \
+	do { \
+		if ((o)->verbosity >= (v)) { \
+			printf(__VA_ARGS__); \
+			puts(""); \
+		} \
+	} while (0)
+
+int notes_merge(struct notes_merge_options *o,
+		unsigned char *result_sha1)
+{
+	unsigned char local_sha1[20], remote_sha1[20];
+	struct commit *local, *remote;
+	struct commit_list *bases = NULL;
+	const unsigned char *base_sha1;
+	int result = 0;
+
+	assert(o->local_ref && o->remote_ref);
+	hashclr(result_sha1);
+
+	trace_printf("notes_merge(o->local_ref = %s, o->remote_ref = %s)\n",
+	       o->local_ref, o->remote_ref);
+
+	/* Dereference o->local_ref into local_sha1 */
+	if (!resolve_ref(o->local_ref, local_sha1, 0, NULL))
+		die("Failed to resolve local notes ref '%s'", o->local_ref);
+	else if (!check_ref_format(o->local_ref) && is_null_sha1(local_sha1))
+		local = NULL; /* local_sha1 == null_sha1 indicates unborn ref */
+	else if (!(local = lookup_commit_reference(local_sha1)))
+		die("Could not parse local commit %s (%s)",
+		    sha1_to_hex(local_sha1), o->local_ref);
+	trace_printf("\tlocal commit: %.7s\n", sha1_to_hex(local_sha1));
+
+	/* Dereference o->remote_ref into remote_sha1 */
+	if (get_sha1(o->remote_ref, remote_sha1)) {
+		/*
+		 * Failed to get remote_sha1. If o->remote_ref looks like an
+		 * unborn ref, perform the merge using an empty notes tree.
+		 */
+		if (!check_ref_format(o->remote_ref)) {
+			hashclr(remote_sha1);
+			remote = NULL;
+		}
+		else
+			die("Failed to resolve remote notes ref '%s'",
+			    o->remote_ref);
+	}
+	else if (!(remote = lookup_commit_reference(remote_sha1)))
+		die("Could not parse remote commit %s (%s)",
+		    sha1_to_hex(remote_sha1), o->remote_ref);
+	trace_printf("\tremote commit: %.7s\n", sha1_to_hex(remote_sha1));
+
+	if (!local && !remote)
+		die("Cannot merge empty notes ref (%s) into empty notes ref "
+		    "(%s)", o->remote_ref, o->local_ref);
+	if (!local) {
+		/* result == remote commit */
+		hashcpy(result_sha1, remote_sha1);
+		goto found_result;
+	}
+	if (!remote) {
+		/* result == local commit */
+		hashcpy(result_sha1, local_sha1);
+		goto found_result;
+	}
+	assert(local && remote);
+
+	/* Find merge bases */
+	bases = get_merge_bases(local, remote, 1);
+	if (!bases) {
+		base_sha1 = null_sha1;
+		OUTPUT(o, 4, "No merge base found; doing history-less merge");
+	} else if (!bases->next) {
+		base_sha1 = bases->item->object.sha1;
+		OUTPUT(o, 4, "One merge base found (%.7s)",
+		       sha1_to_hex(base_sha1));
+	} else {
+		/* TODO: How to handle multiple merge-bases? */
+		base_sha1 = bases->item->object.sha1;
+		OUTPUT(o, 3, "Multiple merge bases found. Using the first "
+		       "(%.7s)", sha1_to_hex(base_sha1));
+	}
+
+	OUTPUT(o, 4, "Merging remote commit %.7s into local commit %.7s with "
+	       "merge-base %.7s", sha1_to_hex(remote->object.sha1),
+	       sha1_to_hex(local->object.sha1), sha1_to_hex(base_sha1));
+
+	if (!hashcmp(remote->object.sha1, base_sha1)) {
+		/* Already merged; result == local commit */
+		OUTPUT(o, 2, "Already up-to-date!");
+		hashcpy(result_sha1, local->object.sha1);
+		goto found_result;
+	}
+	if (!hashcmp(local->object.sha1, base_sha1)) {
+		/* Fast-forward; result == remote commit */
+		OUTPUT(o, 2, "Fast-forward");
+		hashcpy(result_sha1, remote->object.sha1);
+		goto found_result;
+	}
+
+	/* TODO: */
+	result = error("notes_merge() cannot yet handle real merges.");
+
+found_result:
+	free_commit_list(bases);
+	trace_printf("notes_merge(): result = %i, result_sha1 = %.7s\n",
+	       result, sha1_to_hex(result_sha1));
+	return result;
+}
diff --git a/notes-merge.h b/notes-merge.h
new file mode 100644
index 0000000..fd572ac
--- /dev/null
+++ b/notes-merge.h
@@ -0,0 +1,36 @@
+#ifndef NOTES_MERGE_H
+#define NOTES_MERGE_H
+
+enum notes_merge_verbosity {
+	NOTES_MERGE_VERBOSITY_DEFAULT = 2,
+	NOTES_MERGE_VERBOSITY_MAX = 5
+};
+
+struct notes_merge_options {
+	const char *local_ref;
+	const char *remote_ref;
+	int verbosity;
+};
+
+void init_notes_merge_options(struct notes_merge_options *o);
+
+/*
+ * Merge notes from o->remote_ref into o->local_ref
+ *
+ * The commits given by the two refs are merged, producing one of the following
+ * outcomes:
+ *
+ * 1. The merge trivially results in an existing commit (e.g. fast-forward or
+ *    already-up-to-date). The SHA1 of the result is written into 'result_sha1'
+ *    and 0 is returned.
+ * 2. The merge fails. result_sha1 is set to null_sha1, and non-zero returned.
+ *
+ * Both o->local_ref and o->remote_ref must be given (non-NULL), but either ref
+ * (although not both) may refer to a non-existing notes ref, in which case
+ * that notes ref is interpreted as an empty notes tree, and the merge
+ * trivially results in what the other ref points to.
+ */
+int notes_merge(struct notes_merge_options *o,
+		unsigned char *result_sha1);
+
+#endif
diff --git a/t/t3308-notes-merge.sh b/t/t3308-notes-merge.sh
new file mode 100755
index 0000000..9acb684
--- /dev/null
+++ b/t/t3308-notes-merge.sh
@@ -0,0 +1,180 @@
+#!/bin/sh
+#
+# Copyright (c) 2010 Johan Herland
+#
+
+test_description='Test merging of notes trees'
+
+. ./test-lib.sh
+
+test_expect_success setup '
+	test_commit 1st &&
+	test_commit 2nd &&
+	test_commit 3rd &&
+	test_commit 4th &&
+	test_commit 5th &&
+	# Create notes on 4 first commits
+	git config core.notesRef refs/notes/x &&
+	git notes add -m "Notes on 1st commit" 1st &&
+	git notes add -m "Notes on 2nd commit" 2nd &&
+	git notes add -m "Notes on 3rd commit" 3rd &&
+	git notes add -m "Notes on 4th commit" 4th
+'
+
+commit_sha1=$(git rev-parse 1st^{commit})
+commit_sha2=$(git rev-parse 2nd^{commit})
+commit_sha3=$(git rev-parse 3rd^{commit})
+commit_sha4=$(git rev-parse 4th^{commit})
+commit_sha5=$(git rev-parse 5th^{commit})
+
+verify_notes () {
+	notes_ref="$1"
+	git -c core.notesRef="refs/notes/$notes_ref" notes |
+		sort >"output_notes_$notes_ref" &&
+	test_cmp "expect_notes_$notes_ref" "output_notes_$notes_ref" &&
+	git -c core.notesRef="refs/notes/$notes_ref" log --format="%H %s%n%N" \
+		>"output_log_$notes_ref" &&
+	test_cmp "expect_log_$notes_ref" "output_log_$notes_ref"
+}
+
+cat <<EOF | sort >expect_notes_x
+5e93d24084d32e1cb61f7070505b9d2530cca987 $commit_sha4
+8366731eeee53787d2bdf8fc1eff7d94757e8da0 $commit_sha3
+eede89064cd42441590d6afec6c37b321ada3389 $commit_sha2
+daa55ffad6cb99bf64226532147ffcaf5ce8bdd1 $commit_sha1
+EOF
+
+cat >expect_log_x <<EOF
+$commit_sha5 5th
+
+$commit_sha4 4th
+Notes on 4th commit
+
+$commit_sha3 3rd
+Notes on 3rd commit
+
+$commit_sha2 2nd
+Notes on 2nd commit
+
+$commit_sha1 1st
+Notes on 1st commit
+
+EOF
+
+test_expect_success 'verify initial notes (x)' '
+	verify_notes x
+'
+
+cp expect_notes_x expect_notes_y
+cp expect_log_x expect_log_y
+
+test_expect_success 'fail to merge empty notes ref into empty notes ref (z => y)' '
+	test_must_fail git -c "core.notesRef=refs/notes/y" notes merge z
+'
+
+test_expect_success 'fail to merge into various non-notes refs' '
+	test_must_fail git -c "core.notesRef=refs/notes" notes merge x &&
+	test_must_fail git -c "core.notesRef=refs/notes/" notes merge x &&
+	mkdir -p .git/refs/notes/dir &&
+	test_must_fail git -c "core.notesRef=refs/notes/dir" notes merge x &&
+	test_must_fail git -c "core.notesRef=refs/notes/dir/" notes merge x &&
+	test_must_fail git -c "core.notesRef=refs/heads/master" notes merge x &&
+	test_must_fail git -c "core.notesRef=refs/notes/y:" notes merge x &&
+	test_must_fail git -c "core.notesRef=refs/notes/y:foo" notes merge x &&
+	test_must_fail git -c "core.notesRef=refs/notes/foo^{bar" notes merge x
+'
+
+test_expect_success 'fail to merge various non-note-trees' '
+	git config core.notesRef refs/notes/y &&
+	test_must_fail git notes merge refs/notes &&
+	test_must_fail git notes merge refs/notes/ &&
+	test_must_fail git notes merge refs/notes/dir &&
+	test_must_fail git notes merge refs/notes/dir/ &&
+	test_must_fail git notes merge refs/heads/master &&
+	test_must_fail git notes merge x: &&
+	test_must_fail git notes merge x:foo &&
+	test_must_fail git notes merge foo^{bar
+'
+
+test_expect_success 'merge notes into empty notes ref (x => y)' '
+	git config core.notesRef refs/notes/y &&
+	git notes merge x &&
+	verify_notes y &&
+	# x and y should point to the same notes commit
+	test "$(git rev-parse refs/notes/x)" = "$(git rev-parse refs/notes/y)"
+'
+
+test_expect_success 'merge empty notes ref (z => y)' '
+	git notes merge z &&
+	# y should not change (still == x)
+	test "$(git rev-parse refs/notes/x)" = "$(git rev-parse refs/notes/y)"
+'
+
+test_expect_success 'change notes on other notes ref (y)' '
+	# Not touching notes to 1st commit
+	git notes remove 2nd &&
+	git notes append -m "More notes on 3rd commit" 3rd &&
+	git notes add -f -m "New notes on 4th commit" 4th &&
+	git notes add -m "Notes on 5th commit" 5th
+'
+
+test_expect_success 'merge previous notes commit (y^ => y) => No-op' '
+	pre_state="$(git rev-parse refs/notes/y)" &&
+	git notes merge y^ &&
+	# y should not move
+	test "$pre_state" = "$(git rev-parse refs/notes/y)"
+'
+
+cat <<EOF | sort >expect_notes_y
+0f2efbd00262f2fd41dfae33df8765618eeacd99 $commit_sha5
+dec2502dac3ea161543f71930044deff93fa945c $commit_sha4
+4069cdb399fd45463ec6eef8e051a16a03592d91 $commit_sha3
+daa55ffad6cb99bf64226532147ffcaf5ce8bdd1 $commit_sha1
+EOF
+
+cat >expect_log_y <<EOF
+$commit_sha5 5th
+Notes on 5th commit
+
+$commit_sha4 4th
+New notes on 4th commit
+
+$commit_sha3 3rd
+Notes on 3rd commit
+
+More notes on 3rd commit
+
+$commit_sha2 2nd
+
+$commit_sha1 1st
+Notes on 1st commit
+
+EOF
+
+test_expect_success 'verify changed notes on other notes ref (y)' '
+	verify_notes y
+'
+
+test_expect_success 'verify unchanged notes on original notes ref (x)' '
+	verify_notes x
+'
+
+test_expect_success 'merge original notes (x) into changed notes (y) => No-op' '
+	git notes merge -vvv x &&
+	verify_notes y &&
+	verify_notes x
+'
+
+cp expect_notes_y expect_notes_x
+cp expect_log_y expect_log_x
+
+test_expect_success 'merge changed (y) into original (x) => Fast-forward' '
+	git config core.notesRef refs/notes/x &&
+	git notes merge y &&
+	verify_notes x &&
+	verify_notes y &&
+	# x and y should point to same the notes commit
+	test "$(git rev-parse refs/notes/x)" = "$(git rev-parse refs/notes/y)"
+'
+
+test_done
-- 
1.7.3.98.g5ad7d9

[PATCHv5 11/23] builtin/notes.c: Refactor creation of notes commits.

[Johan Herland]

Create new function create_notes_commit() which is slightly more general than
commit_notes() (accepts multiple commit parents and does not auto-update the
notes ref). This function will be used by the notes-merge functionality in
future patches.

Also rewrite builtin/notes.c:commit_notes() to reuse this new function.

Signed-off-by: Johan Herland <johan@herland.net>
---
 builtin.h       |    2 +-
 builtin/notes.c |   28 +++++-----------------------
 notes-merge.c   |   27 +++++++++++++++++++++++++++
 notes-merge.h   |   14 ++++++++++++++
 4 files changed, 47 insertions(+), 24 deletions(-)

diff --git a/builtin.h b/builtin.h
index ed6ee26..908d850 100644
--- a/builtin.h
+++ b/builtin.h
@@ -17,7 +17,7 @@ extern void prune_packed_objects(int);
 extern int fmt_merge_msg(int merge_summary, struct strbuf *in,
 	struct strbuf *out);
 extern int fmt_merge_msg_shortlog(struct strbuf *in, struct strbuf *out);
-extern int commit_notes(struct notes_tree *t, const char *msg);
+extern void commit_notes(struct notes_tree *t, const char *msg);
 
 struct notes_rewrite_cfg {
 	struct notes_tree **trees;
diff --git a/builtin/notes.c b/builtin/notes.c
index fbabdc7..97d8baa 100644
--- a/builtin/notes.c
+++ b/builtin/notes.c
@@ -288,18 +288,17 @@ static int parse_reedit_arg(const struct option *opt, const char *arg, int unset
 	return parse_reuse_arg(opt, arg, unset);
 }
 
-int commit_notes(struct notes_tree *t, const char *msg)
+void commit_notes(struct notes_tree *t, const char *msg)
 {
-	struct commit_list *parent;
-	unsigned char tree_sha1[20], prev_commit[20], new_commit[20];
 	struct strbuf buf = STRBUF_INIT;
+	unsigned char commit_sha1[20];
 
 	if (!t)
 		t = &default_notes_tree;
 	if (!t->initialized || !t->ref || !*t->ref)
 		die("Cannot commit uninitialized/unreferenced notes tree");
 	if (!t->dirty)
-		return 0; /* don't have to commit an unchanged tree */
+		return; /* don't have to commit an unchanged tree */
 
 	/* Prepare commit message and reflog message */
 	strbuf_addstr(&buf, "notes: "); /* commit message starts at index 7 */
@@ -307,27 +306,10 @@ int commit_notes(struct notes_tree *t, const char *msg)
 	if (buf.buf[buf.len - 1] != '\n')
 		strbuf_addch(&buf, '\n'); /* Make sure msg ends with newline */
 
-	/* Convert notes tree to tree object */
-	if (write_notes_tree(t, tree_sha1))
-		die("Failed to write current notes tree to database");
-
-	/* Create new commit for the tree object */
-	if (!read_ref(t->ref, prev_commit)) { /* retrieve parent commit */
-		parent = xmalloc(sizeof(*parent));
-		parent->item = lookup_commit(prev_commit);
-		parent->next = NULL;
-	} else {
-		hashclr(prev_commit);
-		parent = NULL;
-	}
-	if (commit_tree(buf.buf + 7, tree_sha1, parent, new_commit, NULL))
-		die("Failed to commit notes tree to database");
-
-	/* Update notes ref with new commit */
-	update_ref(buf.buf, t->ref, new_commit, prev_commit, 0, DIE_ON_ERR);
+	create_notes_commit(t, NULL, buf.buf + 7, commit_sha1);
+	update_ref(buf.buf, t->ref, commit_sha1, NULL, 0, DIE_ON_ERR);
 
 	strbuf_release(&buf);
-	return 0;
 }
 
 combine_notes_fn parse_combine_notes_fn(const char *v)
diff --git a/notes-merge.c b/notes-merge.c
index cd917f9..6ffa6e7 100644
--- a/notes-merge.c
+++ b/notes-merge.c
@@ -1,6 +1,7 @@
 #include "cache.h"
 #include "commit.h"
 #include "refs.h"
+#include "notes.h"
 #include "notes-merge.h"
 
 void init_notes_merge_options(struct notes_merge_options *o)
@@ -17,6 +18,32 @@ void init_notes_merge_options(struct notes_merge_options *o)
 		} \
 	} while (0)
 
+void create_notes_commit(struct notes_tree *t, struct commit_list *parents,
+			 const char *msg, unsigned char *result_sha1)
+{
+	unsigned char tree_sha1[20];
+
+	assert(t->initialized);
+
+	if (write_notes_tree(t, tree_sha1))
+		die("Failed to write notes tree to database");
+
+	if (!parents) {
+		/* Deduce parent commit from t->ref */
+		unsigned char parent_sha1[20];
+		if (!read_ref(t->ref, parent_sha1)) {
+			struct commit *parent = lookup_commit(parent_sha1);
+			if (!parent || parse_commit(parent))
+				die("Failed to find/parse commit %s", t->ref);
+			commit_list_insert(parent, &parents);
+		}
+		/* else: t->ref points to nothing, assume root/orphan commit */
+	}
+
+	if (commit_tree(msg, tree_sha1, parents, result_sha1, NULL))
+		die("Failed to commit notes tree to database");
+}
+
 int notes_merge(struct notes_merge_options *o,
 		unsigned char *result_sha1)
 {
diff --git a/notes-merge.h b/notes-merge.h
index fd572ac..49e1b3a 100644
--- a/notes-merge.h
+++ b/notes-merge.h
@@ -15,6 +15,20 @@ struct notes_merge_options {
 void init_notes_merge_options(struct notes_merge_options *o);
 
 /*
+ * Create new notes commit from the given notes tree
+ *
+ * Properties of the created commit:
+ * - tree: the result of converting t to a tree object with write_notes_tree().
+ * - parents: the given parents OR (if NULL) the commit referenced by t->ref.
+ * - author/committer: the default determined by commmit_tree().
+ * - commit message: msg
+ *
+ * The resulting commit SHA1 is stored in result_sha1.
+ */
+void create_notes_commit(struct notes_tree *t, struct commit_list *parents,
+			 const char *msg, unsigned char *result_sha1);
+
+/*
  * Merge notes from o->remote_ref into o->local_ref
  *
  * The commits given by the two refs are merged, producing one of the following
-- 
1.7.3.98.g5ad7d9

[PATCHv5 12/23] git notes merge: Handle real, non-conflicting notes merges

[Johan Herland]

This continuation of the 'git notes merge' implementation teaches notes-merge
to properly do real merges between notes trees: Two diffs are performed, one
from $base to $remote, and another from $base to $local. The paths in each
diff are normalized to SHA1 object names. The two diffs are then consolidated
into a single list of change pairs to be evaluated. Each change pair consist
of:

  - The annotated object's SHA1
  - The $base SHA1 (i.e. the common ancestor notes for this object)
  - The $local SHA1 (i.e. the current notes for this object)
  - The $remote SHA1 (i.e. the to-be-merged notes for this object)

>From the pair ($base -> $local, $base -> $remote), we can determine the merge
result using regular 3-way rules. If conflicts are encountered in this
process, we fail loudly and exit (conflict handling to be added in a future
patch), If we can complete the merge without conflicts, the resulting
notes tree is committed, and the current notes ref updated.

The patch includes added testcases verifying that we can successfully do real
conflict-less merges.

This patch has been improved by the following contributions:
- Jonathan Nieder: Future-proof by always checking add_note() return value
- Stephen Boyd: Use test_commit
- Jonathan Nieder: Use trace_printf(...) instead of OUTPUT(o, 5, ...)

Thanks-to: Jonathan Nieder <jrnieder@gmail.com>
Thanks-to: Stephen Boyd <bebarino@gmail.com>
Signed-off-by: Johan Herland <johan@herland.net>
---
 builtin/notes.c        |   15 ++-
 notes-merge.c          |  325 +++++++++++++++++++++++++++++++++++++++++++++++-
 notes-merge.h          |   15 ++-
 t/t3308-notes-merge.sh |  188 ++++++++++++++++++++++++++++
 4 files changed, 532 insertions(+), 11 deletions(-)

diff --git a/builtin/notes.c b/builtin/notes.c
index 97d8baa..c967b23 100644
--- a/builtin/notes.c
+++ b/builtin/notes.c
@@ -765,6 +765,7 @@ static int merge(int argc, const char **argv, const char *prefix)
 {
 	struct strbuf remote_ref = STRBUF_INIT, msg = STRBUF_INIT;
 	unsigned char result_sha1[20];
+	struct notes_tree *t;
 	struct notes_merge_options o;
 	int verbosity = 0, result;
 	struct option options[] = {
@@ -788,19 +789,23 @@ static int merge(int argc, const char **argv, const char *prefix)
 	expand_notes_ref(&remote_ref);
 	o.remote_ref = remote_ref.buf;
 
-	result = notes_merge(&o, result_sha1);
+	t = init_notes_check("merge");
 
 	strbuf_addf(&msg, "notes: Merged notes from %s into %s",
 		    remote_ref.buf, default_notes_ref());
-	if (result == 0) { /* Merge resulted (trivially) in result_sha1 */
+	o.commit_msg = msg.buf + 7; // skip "notes: " prefix
+
+	result = notes_merge(&o, t, result_sha1);
+
+	if (result >= 0) /* Merge resulted (trivially) in result_sha1 */
 		/* Update default notes ref with new commit */
 		update_ref(msg.buf, default_notes_ref(), result_sha1, NULL,
 			   0, DIE_ON_ERR);
-	} else {
+	else
 		/* TODO: */
-		die("'git notes merge' cannot yet handle non-trivial merges!");
-	}
+		die("'git notes merge' cannot yet handle conflicts!");
 
+	free_notes(t);
 	strbuf_release(&remote_ref);
 	strbuf_release(&msg);
 	return 0;
diff --git a/notes-merge.c b/notes-merge.c
index 6ffa6e7..20db0b6 100644
--- a/notes-merge.c
+++ b/notes-merge.c
@@ -1,9 +1,15 @@
 #include "cache.h"
 #include "commit.h"
 #include "refs.h"
+#include "diff.h"
+#include "diffcore.h"
 #include "notes.h"
 #include "notes-merge.h"
 
+struct notes_merge_pair {
+	unsigned char obj[20], base[20], local[20], remote[20];
+};
+
 void init_notes_merge_options(struct notes_merge_options *o)
 {
 	memset(o, 0, sizeof(struct notes_merge_options));
@@ -18,6 +24,305 @@ void init_notes_merge_options(struct notes_merge_options *o)
 		} \
 	} while (0)
 
+static int path_to_sha1(const char *path, unsigned char *sha1)
+{
+	char hex_sha1[40];
+	int i = 0;
+	while (*path && i < 40) {
+		if (*path != '/')
+			hex_sha1[i++] = *path;
+		path++;
+	}
+	if (*path || i != 40)
+		return -1;
+	return get_sha1_hex(hex_sha1, sha1);
+}
+
+static int verify_notes_filepair(struct diff_filepair *p, unsigned char *sha1)
+{
+	switch (p->status) {
+	case DIFF_STATUS_MODIFIED:
+		assert(p->one->mode == p->two->mode);
+		assert(!is_null_sha1(p->one->sha1));
+		assert(!is_null_sha1(p->two->sha1));
+		break;
+	case DIFF_STATUS_ADDED:
+		assert(is_null_sha1(p->one->sha1));
+		break;
+	case DIFF_STATUS_DELETED:
+		assert(is_null_sha1(p->two->sha1));
+		break;
+	default:
+		return -1;
+	}
+	assert(!strcmp(p->one->path, p->two->path));
+	return path_to_sha1(p->one->path, sha1);
+}
+
+static struct notes_merge_pair *find_notes_merge_pair_pos(
+		struct notes_merge_pair *list, int len, unsigned char *obj,
+		int insert_new, int *occupied)
+{
+	/*
+	 * Both diff_tree_remote() and diff_tree_local() tend to process
+	 * merge_pairs in ascending order. Therefore, cache last returned
+	 * index, and search sequentially from there until the appropriate
+	 * position is found.
+	 *
+	 * Since inserts only happen from diff_tree_remote() (which mainly
+	 * _appends_), we don't care that inserting into the middle of the
+	 * list is expensive (using memmove()).
+	 */
+	static int last_index = 0;
+	int i = last_index < len ? last_index : len - 1;
+	int prev_cmp = 0, cmp = -1;
+	while (i >= 0 && i < len) {
+		cmp = hashcmp(obj, list[i].obj);
+		if (!cmp) /* obj belongs @ i */
+			break;
+		else if (cmp < 0 && prev_cmp <= 0) /* obj belongs < i */
+			i--;
+		else if (cmp < 0) /* obj belongs between i-1 and i */
+			break;
+		else if (cmp > 0 && prev_cmp >= 0) /* obj belongs > i */
+			i++;
+		else /* if (cmp > 0) */ { /* obj belongs between i and i+1 */
+			i++;
+			break;
+		}
+		prev_cmp = cmp;
+	}
+	if (i < 0)
+		i = 0;
+	/* obj belongs at, or immediately preceding, index i (0 <= i <= len) */
+
+	if (!cmp)
+		*occupied = 1;
+	else {
+		*occupied = 0;
+		if (insert_new && i < len) {
+			memmove(list + i + 1, list + i,
+				(len - i) * sizeof(struct notes_merge_pair));
+			memset(list + i, 0, sizeof(struct notes_merge_pair));
+		}
+	}
+	last_index = i;
+	return list + i;
+}
+
+static unsigned char uninitialized[20] =
+	"\xff\xff\xff\xff\xff\xff\xff\xff\xff\xff" \
+	"\xff\xff\xff\xff\xff\xff\xff\xff\xff\xff";
+
+static struct notes_merge_pair *diff_tree_remote(struct notes_merge_options *o,
+						 const unsigned char *base,
+						 const unsigned char *remote,
+						 int *num_changes)
+{
+	struct diff_options opt;
+	struct notes_merge_pair *changes;
+	int i, len = 0;
+
+	trace_printf("\tdiff_tree_remote(base = %.7s, remote = %.7s)\n",
+	       sha1_to_hex(base), sha1_to_hex(remote));
+
+	diff_setup(&opt);
+	DIFF_OPT_SET(&opt, RECURSIVE);
+	opt.output_format = DIFF_FORMAT_NO_OUTPUT;
+	if (diff_setup_done(&opt) < 0)
+		die("diff_setup_done failed");
+	diff_tree_sha1(base, remote, "", &opt);
+	diffcore_std(&opt);
+
+	changes = xcalloc(diff_queued_diff.nr, sizeof(struct notes_merge_pair));
+
+	for (i = 0; i < diff_queued_diff.nr; i++) {
+		struct diff_filepair *p = diff_queued_diff.queue[i];
+		struct notes_merge_pair *mp;
+		int occupied;
+		unsigned char obj[20];
+
+		if (verify_notes_filepair(p, obj)) {
+			trace_printf("\t\tCannot merge entry '%s' (%c): "
+			       "%.7s -> %.7s. Skipping!\n", p->one->path,
+			       p->status, sha1_to_hex(p->one->sha1),
+			       sha1_to_hex(p->two->sha1));
+			continue;
+		}
+		mp = find_notes_merge_pair_pos(changes, len, obj, 1, &occupied);
+		if (occupied) {
+			/* We've found an addition/deletion pair */
+			assert(!hashcmp(mp->obj, obj));
+			if (is_null_sha1(p->one->sha1)) { /* addition */
+				assert(is_null_sha1(mp->remote));
+				hashcpy(mp->remote, p->two->sha1);
+			} else if (is_null_sha1(p->two->sha1)) { /* deletion */
+				assert(is_null_sha1(mp->base));
+				hashcpy(mp->base, p->one->sha1);
+			} else
+				assert(!"Invalid existing change recorded");
+		} else {
+			hashcpy(mp->obj, obj);
+			hashcpy(mp->base, p->one->sha1);
+			hashcpy(mp->local, uninitialized);
+			hashcpy(mp->remote, p->two->sha1);
+			len++;
+		}
+		trace_printf("\t\tStored remote change for %s: %.7s -> %.7s\n",
+		       sha1_to_hex(mp->obj), sha1_to_hex(mp->base),
+		       sha1_to_hex(mp->remote));
+	}
+	diff_flush(&opt);
+	diff_tree_release_paths(&opt);
+
+	*num_changes = len;
+	return changes;
+}
+
+static void diff_tree_local(struct notes_merge_options *o,
+			    struct notes_merge_pair *changes, int len,
+			    const unsigned char *base,
+			    const unsigned char *local)
+{
+	struct diff_options opt;
+	int i;
+
+	trace_printf("\tdiff_tree_local(len = %i, base = %.7s, local = %.7s)\n",
+	       len, sha1_to_hex(base), sha1_to_hex(local));
+
+	diff_setup(&opt);
+	DIFF_OPT_SET(&opt, RECURSIVE);
+	opt.output_format = DIFF_FORMAT_NO_OUTPUT;
+	if (diff_setup_done(&opt) < 0)
+		die("diff_setup_done failed");
+	diff_tree_sha1(base, local, "", &opt);
+	diffcore_std(&opt);
+
+	for (i = 0; i < diff_queued_diff.nr; i++) {
+		struct diff_filepair *p = diff_queued_diff.queue[i];
+		struct notes_merge_pair *mp;
+		int match;
+		unsigned char obj[20];
+
+		if (verify_notes_filepair(p, obj)) {
+			trace_printf("\t\tCannot merge entry '%s' (%c): "
+			       "%.7s -> %.7s. Skipping!\n", p->one->path,
+			       p->status, sha1_to_hex(p->one->sha1),
+			       sha1_to_hex(p->two->sha1));
+			continue;
+		}
+		mp = find_notes_merge_pair_pos(changes, len, obj, 0, &match);
+		if (!match) {
+			trace_printf("\t\tIgnoring local-only change for %s: "
+			       "%.7s -> %.7s\n", sha1_to_hex(obj),
+			       sha1_to_hex(p->one->sha1),
+			       sha1_to_hex(p->two->sha1));
+			continue;
+		}
+
+		assert(!hashcmp(mp->obj, obj));
+		if (is_null_sha1(p->two->sha1)) { /* deletion */
+			/*
+			 * Either this is a true deletion (1), or it is part
+			 * of an A/D pair (2), or D/A pair (3):
+			 *
+			 * (1) mp->local is uninitialized; set it to null_sha1
+			 * (2) mp->local is not uninitialized; don't touch it
+			 * (3) mp->local is uninitialized; set it to null_sha1
+			 *     (will be overwritten by following addition)
+			 */
+			if (!hashcmp(mp->local, uninitialized))
+				hashclr(mp->local);
+		} else if (is_null_sha1(p->one->sha1)) { /* addition */
+			/*
+			 * Either this is a true addition (1), or it is part
+			 * of an A/D pair (2), or D/A pair (3):
+			 *
+			 * (1) mp->local is uninitialized; set to p->two->sha1
+			 * (2) mp->local is uninitialized; set to p->two->sha1
+			 * (3) mp->local is null_sha1;     set to p->two->sha1
+			 */
+			assert(is_null_sha1(mp->local) ||
+			       !hashcmp(mp->local, uninitialized));
+			hashcpy(mp->local, p->two->sha1);
+		} else { /* modification */
+			/*
+			 * This is a true modification. p->one->sha1 shall
+			 * match mp->base, and mp->local shall be uninitialized.
+			 * Set mp->local to p->two->sha1.
+			 */
+			assert(!hashcmp(p->one->sha1, mp->base));
+			assert(!hashcmp(mp->local, uninitialized));
+			hashcpy(mp->local, p->two->sha1);
+		}
+		trace_printf("\t\tStored local change for %s: %.7s -> %.7s\n",
+		       sha1_to_hex(mp->obj), sha1_to_hex(mp->base),
+		       sha1_to_hex(mp->local));
+	}
+	diff_flush(&opt);
+	diff_tree_release_paths(&opt);
+}
+
+static int merge_changes(struct notes_merge_options *o,
+			 struct notes_merge_pair *changes, int *num_changes,
+			 struct notes_tree *t)
+{
+	int i, conflicts = 0;
+
+	trace_printf("\tmerge_changes(num_changes = %i)\n", *num_changes);
+	for (i = 0; i < *num_changes; i++) {
+		struct notes_merge_pair *p = changes + i;
+		trace_printf("\t\t%.7s: %.7s -> %.7s/%.7s\n",
+		       sha1_to_hex(p->obj), sha1_to_hex(p->base),
+		       sha1_to_hex(p->local), sha1_to_hex(p->remote));
+
+		if (!hashcmp(p->base, p->remote)) {
+			/* no remote change; nothing to do */
+			trace_printf("\t\t\tskipping (no remote change)\n");
+		} else if (!hashcmp(p->local, p->remote)) {
+			/* same change in local and remote; nothing to do */
+			trace_printf("\t\t\tskipping (local == remote)\n");
+		} else if (!hashcmp(p->local, uninitialized) ||
+			   !hashcmp(p->local, p->base)) {
+			/* no local change; adopt remote change */
+			trace_printf("\t\t\tno local change, adopted remote\n");
+			if (add_note(t, p->obj, p->remote,
+				     combine_notes_overwrite))
+				die("confused: combine_notes_overwrite failed");
+		} else {
+			/* need file-level merge between local and remote */
+			trace_printf("\t\t\tneed content-level merge\n");
+			conflicts += 1; /* TODO */
+		}
+	}
+
+	return conflicts;
+}
+
+static int merge_from_diffs(struct notes_merge_options *o,
+			    const unsigned char *base,
+			    const unsigned char *local,
+			    const unsigned char *remote, struct notes_tree *t)
+{
+	struct notes_merge_pair *changes;
+	int num_changes, conflicts;
+
+	trace_printf("\tmerge_from_diffs(base = %.7s, local = %.7s, "
+	       "remote = %.7s)\n", sha1_to_hex(base), sha1_to_hex(local),
+	       sha1_to_hex(remote));
+
+	changes = diff_tree_remote(o, base, remote, &num_changes);
+	diff_tree_local(o, changes, num_changes, base, local);
+
+	conflicts = merge_changes(o, changes, &num_changes, t);
+	free(changes);
+
+	OUTPUT(o, 4, "Merge result: %i unmerged notes and a %s notes tree",
+	       conflicts, t->dirty ? "dirty" : "clean");
+
+	return conflicts ? -1 : 1;
+}
+
 void create_notes_commit(struct notes_tree *t, struct commit_list *parents,
 			 const char *msg, unsigned char *result_sha1)
 {
@@ -45,15 +350,17 @@ void create_notes_commit(struct notes_tree *t, struct commit_list *parents,
 }
 
 int notes_merge(struct notes_merge_options *o,
+		struct notes_tree *local_tree,
 		unsigned char *result_sha1)
 {
 	unsigned char local_sha1[20], remote_sha1[20];
 	struct commit *local, *remote;
 	struct commit_list *bases = NULL;
-	const unsigned char *base_sha1;
+	const unsigned char *base_sha1, *base_tree_sha1;
 	int result = 0;
 
 	assert(o->local_ref && o->remote_ref);
+	assert(!strcmp(o->local_ref, local_tree->ref));
 	hashclr(result_sha1);
 
 	trace_printf("notes_merge(o->local_ref = %s, o->remote_ref = %s)\n",
@@ -107,14 +414,17 @@ int notes_merge(struct notes_merge_options *o,
 	bases = get_merge_bases(local, remote, 1);
 	if (!bases) {
 		base_sha1 = null_sha1;
+		base_tree_sha1 = (unsigned char *)EMPTY_TREE_SHA1_BIN;
 		OUTPUT(o, 4, "No merge base found; doing history-less merge");
 	} else if (!bases->next) {
 		base_sha1 = bases->item->object.sha1;
+		base_tree_sha1 = bases->item->tree->object.sha1;
 		OUTPUT(o, 4, "One merge base found (%.7s)",
 		       sha1_to_hex(base_sha1));
 	} else {
 		/* TODO: How to handle multiple merge-bases? */
 		base_sha1 = bases->item->object.sha1;
+		base_tree_sha1 = bases->item->tree->object.sha1;
 		OUTPUT(o, 3, "Multiple merge bases found. Using the first "
 		       "(%.7s)", sha1_to_hex(base_sha1));
 	}
@@ -136,8 +446,17 @@ int notes_merge(struct notes_merge_options *o,
 		goto found_result;
 	}
 
-	/* TODO: */
-	result = error("notes_merge() cannot yet handle real merges.");
+	result = merge_from_diffs(o, base_tree_sha1, local->tree->object.sha1,
+				  remote->tree->object.sha1, local_tree);
+
+	if (result > 0) { /* successful non-trivial merge */
+		/* Commit result */
+		struct commit_list *parents = NULL;
+		commit_list_insert(remote, &parents); /* LIFO order */
+		commit_list_insert(local, &parents);
+		create_notes_commit(local_tree, parents, o->commit_msg,
+				    result_sha1);
+	}
 
 found_result:
 	free_commit_list(bases);
diff --git a/notes-merge.h b/notes-merge.h
index 49e1b3a..577cfb3 100644
--- a/notes-merge.h
+++ b/notes-merge.h
@@ -9,6 +9,7 @@ enum notes_merge_verbosity {
 struct notes_merge_options {
 	const char *local_ref;
 	const char *remote_ref;
+	const char *commit_msg;
 	int verbosity;
 };
 
@@ -31,13 +32,20 @@ void create_notes_commit(struct notes_tree *t, struct commit_list *parents,
 /*
  * Merge notes from o->remote_ref into o->local_ref
  *
+ * The given notes_tree 'local_tree' must be the notes_tree referenced by the
+ * o->local_ref. This is the notes_tree in which the object-level merge is
+ * performed.
+ *
  * The commits given by the two refs are merged, producing one of the following
  * outcomes:
  *
  * 1. The merge trivially results in an existing commit (e.g. fast-forward or
- *    already-up-to-date). The SHA1 of the result is written into 'result_sha1'
- *    and 0 is returned.
- * 2. The merge fails. result_sha1 is set to null_sha1, and non-zero returned.
+ *    already-up-to-date). 'local_tree' is untouched, the SHA1 of the result
+ *    is written into 'result_sha1' and 0 is returned.
+ * 2. The merge successfully completes, producing a merge commit. local_tree
+ *    contains the updated notes tree, the SHA1 of the resulting commit is
+ *    written into 'result_sha1', and 1 is returned.
+ * 3. The merge fails. result_sha1 is set to null_sha1, and -1 is returned.
  *
  * Both o->local_ref and o->remote_ref must be given (non-NULL), but either ref
  * (although not both) may refer to a non-existing notes ref, in which case
@@ -45,6 +53,7 @@ void create_notes_commit(struct notes_tree *t, struct commit_list *parents,
  * trivially results in what the other ref points to.
  */
 int notes_merge(struct notes_merge_options *o,
+		struct notes_tree *local_tree,
 		unsigned char *result_sha1);
 
 #endif
diff --git a/t/t3308-notes-merge.sh b/t/t3308-notes-merge.sh
index 9acb684..24d82b4 100755
--- a/t/t3308-notes-merge.sh
+++ b/t/t3308-notes-merge.sh
@@ -177,4 +177,192 @@ test_expect_success 'merge changed (y) into original (x) => Fast-forward' '
 	test "$(git rev-parse refs/notes/x)" = "$(git rev-parse refs/notes/y)"
 '
 
+test_expect_success 'merge empty notes ref (z => y)' '
+	# Prepare empty (but valid) notes ref (z)
+	git config core.notesRef refs/notes/z &&
+	git notes add -m "foo" &&
+	git notes remove &&
+	git notes >output_notes_z &&
+	test_cmp /dev/null output_notes_z &&
+	# Do the merge (z => y)
+	git config core.notesRef refs/notes/y &&
+	git notes merge z &&
+	verify_notes y &&
+	# y should no longer point to the same notes commit as x
+	test "$(git rev-parse refs/notes/x)" != "$(git rev-parse refs/notes/y)"
+'
+
+cat <<EOF | sort >expect_notes_y
+0f2efbd00262f2fd41dfae33df8765618eeacd99 $commit_sha5
+dec2502dac3ea161543f71930044deff93fa945c $commit_sha4
+4069cdb399fd45463ec6eef8e051a16a03592d91 $commit_sha3
+d000d30e6ddcfce3a8122c403226a2ce2fd04d9d $commit_sha2
+43add6bd0c8c0bc871ac7991e0f5573cfba27804 $commit_sha1
+EOF
+
+cat >expect_log_y <<EOF
+$commit_sha5 5th
+Notes on 5th commit
+
+$commit_sha4 4th
+New notes on 4th commit
+
+$commit_sha3 3rd
+Notes on 3rd commit
+
+More notes on 3rd commit
+
+$commit_sha2 2nd
+New notes on 2nd commit
+
+$commit_sha1 1st
+Notes on 1st commit
+
+More notes on 1st commit
+
+EOF
+
+test_expect_success 'change notes on other notes ref (y)' '
+	# Append to 1st commit notes
+	git notes append -m "More notes on 1st commit" 1st &&
+	# Add new notes to 2nd commit
+	git notes add -m "New notes on 2nd commit" 2nd &&
+	verify_notes y
+'
+
+cat <<EOF | sort >expect_notes_x
+0f2efbd00262f2fd41dfae33df8765618eeacd99 $commit_sha5
+1f257a3a90328557c452f0817d6cc50c89d315d4 $commit_sha4
+daa55ffad6cb99bf64226532147ffcaf5ce8bdd1 $commit_sha1
+EOF
+
+cat >expect_log_x <<EOF
+$commit_sha5 5th
+Notes on 5th commit
+
+$commit_sha4 4th
+New notes on 4th commit
+
+More notes on 4th commit
+
+$commit_sha3 3rd
+
+$commit_sha2 2nd
+
+$commit_sha1 1st
+Notes on 1st commit
+
+EOF
+
+test_expect_success 'change notes on notes ref (x)' '
+	git config core.notesRef refs/notes/x &&
+	git notes remove 3rd &&
+	git notes append -m "More notes on 4th commit" 4th &&
+	verify_notes x
+'
+
+cat <<EOF | sort >expect_notes_x
+0f2efbd00262f2fd41dfae33df8765618eeacd99 $commit_sha5
+1f257a3a90328557c452f0817d6cc50c89d315d4 $commit_sha4
+d000d30e6ddcfce3a8122c403226a2ce2fd04d9d $commit_sha2
+43add6bd0c8c0bc871ac7991e0f5573cfba27804 $commit_sha1
+EOF
+
+cat >expect_log_x <<EOF
+$commit_sha5 5th
+Notes on 5th commit
+
+$commit_sha4 4th
+New notes on 4th commit
+
+More notes on 4th commit
+
+$commit_sha3 3rd
+
+$commit_sha2 2nd
+New notes on 2nd commit
+
+$commit_sha1 1st
+Notes on 1st commit
+
+More notes on 1st commit
+
+EOF
+
+test_expect_success 'merge y into x => Non-conflicting 3-way merge' '
+	git notes merge y &&
+	verify_notes x &&
+	verify_notes y
+'
+
+cat <<EOF | sort >expect_notes_w
+05a4927951bcef347f51486575b878b2b60137f2 $commit_sha3
+d000d30e6ddcfce3a8122c403226a2ce2fd04d9d $commit_sha2
+EOF
+
+cat >expect_log_w <<EOF
+$commit_sha5 5th
+
+$commit_sha4 4th
+
+$commit_sha3 3rd
+New notes on 3rd commit
+
+$commit_sha2 2nd
+New notes on 2nd commit
+
+$commit_sha1 1st
+
+EOF
+
+test_expect_success 'create notes on new, separate notes ref (w)' '
+	git config core.notesRef refs/notes/w &&
+	# Add same note as refs/notes/y on 2nd commit
+	git notes add -m "New notes on 2nd commit" 2nd &&
+	# Add new note on 3rd commit (non-conflicting)
+	git notes add -m "New notes on 3rd commit" 3rd &&
+	# Verify state of notes on new, separate notes ref (w)
+	verify_notes w
+'
+
+cat <<EOF | sort >expect_notes_x
+0f2efbd00262f2fd41dfae33df8765618eeacd99 $commit_sha5
+1f257a3a90328557c452f0817d6cc50c89d315d4 $commit_sha4
+05a4927951bcef347f51486575b878b2b60137f2 $commit_sha3
+d000d30e6ddcfce3a8122c403226a2ce2fd04d9d $commit_sha2
+43add6bd0c8c0bc871ac7991e0f5573cfba27804 $commit_sha1
+EOF
+
+cat >expect_log_x <<EOF
+$commit_sha5 5th
+Notes on 5th commit
+
+$commit_sha4 4th
+New notes on 4th commit
+
+More notes on 4th commit
+
+$commit_sha3 3rd
+New notes on 3rd commit
+
+$commit_sha2 2nd
+New notes on 2nd commit
+
+$commit_sha1 1st
+Notes on 1st commit
+
+More notes on 1st commit
+
+EOF
+
+test_expect_success 'merge w into x => Non-conflicting history-less merge' '
+	git config core.notesRef refs/notes/x &&
+	git notes merge w &&
+	# Verify new state of notes on other notes ref (x)
+	verify_notes x &&
+	# Also verify that nothing changed on other notes refs (y and w)
+	verify_notes y &&
+	verify_notes w
+'
+
 test_done
-- 
1.7.3.98.g5ad7d9

[PATCHv5 13/23] git notes merge: Add automatic conflict resolvers (ours, theirs, union)

[Johan Herland]

The new -s/--strategy command-line option to 'git notes merge' allow the user
to choose how notes merge conflicts should be resolved. There are four valid
strategies to choose from:

1. "manual" (the default): This will let the user manually resolve conflicts.
   This option currently fails with an error message. It will be implemented
   properly in future patches.

2. "ours": This automatically chooses the local version of a conflict, and
   discards the remote version.

3. "theirs": This automatically chooses the remote version of a conflict, and
   discards the local version.

4. "union": This automatically resolves the conflict by appending the remote
   version to the local version.

The strategies are implemented using the combine_notes_* functions from the
notes.h API.

The patch also includes testcases verifying the correct implementation of
these strategies.

This patch has been improved by the following contributions:
- Jonathan Nieder: Future-proof by always checking add_note() return value
- Stephen Boyd: Use test_commit
- Stephen Boyd: Use correct option name

Thanks-to: Jonathan Nieder <jrnieder@gmail.com>
Thanks-to: Stephen Boyd <bebarino@gmail.com>
Signed-off-by: Johan Herland <johan@herland.net>
---
 builtin/notes.c                     |   21 ++-
 notes-merge.c                       |   31 ++-
 notes-merge.h                       |    6 +
 t/t3309-notes-merge-auto-resolve.sh |  502 +++++++++++++++++++++++++++++++++++
 4 files changed, 558 insertions(+), 2 deletions(-)
 create mode 100755 t/t3309-notes-merge-auto-resolve.sh

diff --git a/builtin/notes.c b/builtin/notes.c
index c967b23..a249f19 100644
--- a/builtin/notes.c
+++ b/builtin/notes.c
@@ -26,7 +26,7 @@ static const char * const git_notes_usage[] = {
 	"git notes [--ref <notes_ref>] append [-m <msg> | -F <file> | (-c | -C) <object>] [<object>]",
 	"git notes [--ref <notes_ref>] edit [<object>]",
 	"git notes [--ref <notes_ref>] show [<object>]",
-	"git notes [--ref <notes_ref>] merge [-v | -q] <notes_ref>",
+	"git notes [--ref <notes_ref>] merge [-v | -q] [-s <strategy> ] <notes_ref>",
 	"git notes [--ref <notes_ref>] remove [<object>]",
 	"git notes [--ref <notes_ref>] prune [-n | -v]",
 	NULL
@@ -768,8 +768,12 @@ static int merge(int argc, const char **argv, const char *prefix)
 	struct notes_tree *t;
 	struct notes_merge_options o;
 	int verbosity = 0, result;
+	const char *strategy = NULL;
 	struct option options[] = {
 		OPT__VERBOSITY(&verbosity),
+		OPT_STRING('s', "strategy", &strategy, "strategy",
+			   "resolve notes conflicts using the given "
+			   "strategy (manual/ours/theirs/union)"),
 		OPT_END()
 	};
 
@@ -789,6 +793,21 @@ static int merge(int argc, const char **argv, const char *prefix)
 	expand_notes_ref(&remote_ref);
 	o.remote_ref = remote_ref.buf;
 
+	if (strategy) {
+		if (!strcmp(strategy, "manual"))
+			o.strategy = NOTES_MERGE_RESOLVE_MANUAL;
+		else if (!strcmp(strategy, "ours"))
+			o.strategy = NOTES_MERGE_RESOLVE_OURS;
+		else if (!strcmp(strategy, "theirs"))
+			o.strategy = NOTES_MERGE_RESOLVE_THEIRS;
+		else if (!strcmp(strategy, "union"))
+			o.strategy = NOTES_MERGE_RESOLVE_UNION;
+		else {
+			error("Unknown -s/--strategy: %s", strategy);
+			usage_with_options(git_notes_merge_usage, options);
+		}
+	}
+
 	t = init_notes_check("merge");
 
 	strbuf_addf(&msg, "notes: Merged notes from %s into %s",
diff --git a/notes-merge.c b/notes-merge.c
index 20db0b6..f2fa12d 100644
--- a/notes-merge.c
+++ b/notes-merge.c
@@ -263,6 +263,35 @@ static void diff_tree_local(struct notes_merge_options *o,
 	diff_tree_release_paths(&opt);
 }
 
+static int merge_one_change(struct notes_merge_options *o,
+			    struct notes_merge_pair *p, struct notes_tree *t)
+{
+	/*
+	 * Return 0 if change was resolved (and added to notes_tree),
+	 * 1 if conflict
+	 */
+	switch (o->strategy) {
+	case NOTES_MERGE_RESOLVE_MANUAL:
+		return 1;
+	case NOTES_MERGE_RESOLVE_OURS:
+		OUTPUT(o, 2, "Using local notes for %s", sha1_to_hex(p->obj));
+		/* nothing to do */
+		return 0;
+	case NOTES_MERGE_RESOLVE_THEIRS:
+		OUTPUT(o, 2, "Using remote notes for %s", sha1_to_hex(p->obj));
+		if (add_note(t, p->obj, p->remote, combine_notes_overwrite))
+			die("confused: combine_notes_overwrite failed");
+		return 0;
+	case NOTES_MERGE_RESOLVE_UNION:
+		OUTPUT(o, 2, "Concatenating local and remote notes for %s",
+		       sha1_to_hex(p->obj));
+		if (add_note(t, p->obj, p->remote, combine_notes_concatenate))
+			die("confused: combine_notes_concatenate failed");
+		return 0;
+	}
+	die("Unknown strategy (%i).", o->strategy);
+}
+
 static int merge_changes(struct notes_merge_options *o,
 			 struct notes_merge_pair *changes, int *num_changes,
 			 struct notes_tree *t)
@@ -292,7 +321,7 @@ static int merge_changes(struct notes_merge_options *o,
 		} else {
 			/* need file-level merge between local and remote */
 			trace_printf("\t\t\tneed content-level merge\n");
-			conflicts += 1; /* TODO */
+			conflicts += merge_one_change(o, p, t);
 		}
 	}
 
diff --git a/notes-merge.h b/notes-merge.h
index 577cfb3..ed356ae 100644
--- a/notes-merge.h
+++ b/notes-merge.h
@@ -11,6 +11,12 @@ struct notes_merge_options {
 	const char *remote_ref;
 	const char *commit_msg;
 	int verbosity;
+	enum {
+		NOTES_MERGE_RESOLVE_MANUAL = 0,
+		NOTES_MERGE_RESOLVE_OURS,
+		NOTES_MERGE_RESOLVE_THEIRS,
+		NOTES_MERGE_RESOLVE_UNION
+	} strategy;
 };
 
 void init_notes_merge_options(struct notes_merge_options *o);
diff --git a/t/t3309-notes-merge-auto-resolve.sh b/t/t3309-notes-merge-auto-resolve.sh
new file mode 100755
index 0000000..1a1fc7e
--- /dev/null
+++ b/t/t3309-notes-merge-auto-resolve.sh
@@ -0,0 +1,502 @@
+#!/bin/sh
+#
+# Copyright (c) 2010 Johan Herland
+#
+
+test_description='Test notes merging with auto-resolving strategies'
+
+. ./test-lib.sh
+
+# Set up a notes merge scenario with all kinds of potential conflicts
+test_expect_success 'setup commits' '
+	test_commit 1st &&
+	test_commit 2nd &&
+	test_commit 3rd &&
+	test_commit 4th &&
+	test_commit 5th &&
+	test_commit 6th &&
+	test_commit 7th &&
+	test_commit 8th &&
+	test_commit 9th &&
+	test_commit 10th &&
+	test_commit 11th &&
+	test_commit 12th &&
+	test_commit 13th &&
+	test_commit 14th &&
+	test_commit 15th
+'
+
+commit_sha1=$(git rev-parse 1st^{commit})
+commit_sha2=$(git rev-parse 2nd^{commit})
+commit_sha3=$(git rev-parse 3rd^{commit})
+commit_sha4=$(git rev-parse 4th^{commit})
+commit_sha5=$(git rev-parse 5th^{commit})
+commit_sha6=$(git rev-parse 6th^{commit})
+commit_sha7=$(git rev-parse 7th^{commit})
+commit_sha8=$(git rev-parse 8th^{commit})
+commit_sha9=$(git rev-parse 9th^{commit})
+commit_sha10=$(git rev-parse 10th^{commit})
+commit_sha11=$(git rev-parse 11th^{commit})
+commit_sha12=$(git rev-parse 12th^{commit})
+commit_sha13=$(git rev-parse 13th^{commit})
+commit_sha14=$(git rev-parse 14th^{commit})
+commit_sha15=$(git rev-parse 15th^{commit})
+
+verify_notes () {
+	notes_ref="$1"
+	suffix="$2"
+	git -c core.notesRef="refs/notes/$notes_ref" notes |
+		sort >"output_notes_$suffix" &&
+	test_cmp "expect_notes_$suffix" "output_notes_$suffix" &&
+	git -c core.notesRef="refs/notes/$notes_ref" log --format="%H %s%n%N" \
+		>"output_log_$suffix" &&
+	test_cmp "expect_log_$suffix" "output_log_$suffix"
+}
+
+test_expect_success 'setup merge base (x)' '
+	git config core.notesRef refs/notes/x &&
+	git notes add -m "x notes on 6th commit" 6th &&
+	git notes add -m "x notes on 7th commit" 7th &&
+	git notes add -m "x notes on 8th commit" 8th &&
+	git notes add -m "x notes on 9th commit" 9th &&
+	git notes add -m "x notes on 10th commit" 10th &&
+	git notes add -m "x notes on 11th commit" 11th &&
+	git notes add -m "x notes on 12th commit" 12th &&
+	git notes add -m "x notes on 13th commit" 13th &&
+	git notes add -m "x notes on 14th commit" 14th &&
+	git notes add -m "x notes on 15th commit" 15th
+'
+
+cat <<EOF | sort >expect_notes_x
+457a85d6c814ea208550f15fcc48f804ac8dc023 $commit_sha15
+b0c95b954301d69da2bc3723f4cb1680d355937c $commit_sha14
+5d30216a129eeffa97d9694ffe8c74317a560315 $commit_sha13
+dd161bc149470fd890dd4ab52a4cbd79bbd18c36 $commit_sha12
+7abbc45126d680336fb24294f013a7cdfa3ed545 $commit_sha11
+b8d03e173f67f6505a76f6e00cf93440200dd9be $commit_sha10
+20c613c835011c48a5abe29170a2402ca6354910 $commit_sha9
+a3daf8a1e4e5dc3409a303ad8481d57bfea7f5d6 $commit_sha8
+897003322b53bc6ca098e9324ee508362347e734 $commit_sha7
+11d97fdebfa5ceee540a3da07bce6fa0222bc082 $commit_sha6
+EOF
+
+cat >expect_log_x <<EOF
+$commit_sha15 15th
+x notes on 15th commit
+
+$commit_sha14 14th
+x notes on 14th commit
+
+$commit_sha13 13th
+x notes on 13th commit
+
+$commit_sha12 12th
+x notes on 12th commit
+
+$commit_sha11 11th
+x notes on 11th commit
+
+$commit_sha10 10th
+x notes on 10th commit
+
+$commit_sha9 9th
+x notes on 9th commit
+
+$commit_sha8 8th
+x notes on 8th commit
+
+$commit_sha7 7th
+x notes on 7th commit
+
+$commit_sha6 6th
+x notes on 6th commit
+
+$commit_sha5 5th
+
+$commit_sha4 4th
+
+$commit_sha3 3rd
+
+$commit_sha2 2nd
+
+$commit_sha1 1st
+
+EOF
+
+test_expect_success 'verify state of merge base (x)' 'verify_notes x x'
+
+test_expect_success 'setup local branch (y)' '
+	git update-ref refs/notes/y refs/notes/x &&
+	git config core.notesRef refs/notes/y &&
+	git notes add -f -m "y notes on 3rd commit" 3rd &&
+	git notes add -f -m "y notes on 4th commit" 4th &&
+	git notes add -f -m "y notes on 5th commit" 5th &&
+	git notes remove 6th &&
+	git notes remove 7th &&
+	git notes remove 8th &&
+	git notes add -f -m "y notes on 12th commit" 12th &&
+	git notes add -f -m "y notes on 13th commit" 13th &&
+	git notes add -f -m "y notes on 14th commit" 14th &&
+	git notes add -f -m "y notes on 15th commit" 15th
+'
+
+cat <<EOF | sort >expect_notes_y
+68b8630d25516028bed862719855b3d6768d7833 $commit_sha15
+5de7ea7ad4f47e7ff91989fb82234634730f75df $commit_sha14
+3a631fdb6f41b05b55d8f4baf20728ba8f6fccbc $commit_sha13
+a66055fa82f7a03fe0c02a6aba3287a85abf7c62 $commit_sha12
+7abbc45126d680336fb24294f013a7cdfa3ed545 $commit_sha11
+b8d03e173f67f6505a76f6e00cf93440200dd9be $commit_sha10
+20c613c835011c48a5abe29170a2402ca6354910 $commit_sha9
+154508c7a0bcad82b6fe4b472bc4c26b3bf0825b $commit_sha5
+e2bfd06a37dd2031684a59a6e2b033e212239c78 $commit_sha4
+5772f42408c0dd6f097a7ca2d24de0e78d1c46b1 $commit_sha3
+EOF
+
+cat >expect_log_y <<EOF
+$commit_sha15 15th
+y notes on 15th commit
+
+$commit_sha14 14th
+y notes on 14th commit
+
+$commit_sha13 13th
+y notes on 13th commit
+
+$commit_sha12 12th
+y notes on 12th commit
+
+$commit_sha11 11th
+x notes on 11th commit
+
+$commit_sha10 10th
+x notes on 10th commit
+
+$commit_sha9 9th
+x notes on 9th commit
+
+$commit_sha8 8th
+
+$commit_sha7 7th
+
+$commit_sha6 6th
+
+$commit_sha5 5th
+y notes on 5th commit
+
+$commit_sha4 4th
+y notes on 4th commit
+
+$commit_sha3 3rd
+y notes on 3rd commit
+
+$commit_sha2 2nd
+
+$commit_sha1 1st
+
+EOF
+
+test_expect_success 'verify state of local branch (y)' 'verify_notes y y'
+
+test_expect_success 'setup remote branch (z)' '
+	git update-ref refs/notes/z refs/notes/x &&
+	git config core.notesRef refs/notes/z &&
+	git notes add -f -m "z notes on 2nd commit" 2nd &&
+	git notes add -f -m "y notes on 4th commit" 4th &&
+	git notes add -f -m "z notes on 5th commit" 5th &&
+	git notes remove 6th &&
+	git notes add -f -m "z notes on 8th commit" 8th &&
+	git notes remove 9th &&
+	git notes add -f -m "z notes on 11th commit" 11th &&
+	git notes remove 12th &&
+	git notes add -f -m "y notes on 14th commit" 14th &&
+	git notes add -f -m "z notes on 15th commit" 15th
+'
+
+cat <<EOF | sort >expect_notes_z
+9b4b2c61f0615412da3c10f98ff85b57c04ec765 $commit_sha15
+5de7ea7ad4f47e7ff91989fb82234634730f75df $commit_sha14
+5d30216a129eeffa97d9694ffe8c74317a560315 $commit_sha13
+7e3c53503a3db8dd996cb62e37c66e070b44b54d $commit_sha11
+b8d03e173f67f6505a76f6e00cf93440200dd9be $commit_sha10
+851e1638784a884c7dd26c5d41f3340f6387413a $commit_sha8
+897003322b53bc6ca098e9324ee508362347e734 $commit_sha7
+99fc34adfc400b95c67b013115e37e31aa9a6d23 $commit_sha5
+e2bfd06a37dd2031684a59a6e2b033e212239c78 $commit_sha4
+283b48219aee9a4105f6cab337e789065c82c2b9 $commit_sha2
+EOF
+
+cat >expect_log_z <<EOF
+$commit_sha15 15th
+z notes on 15th commit
+
+$commit_sha14 14th
+y notes on 14th commit
+
+$commit_sha13 13th
+x notes on 13th commit
+
+$commit_sha12 12th
+
+$commit_sha11 11th
+z notes on 11th commit
+
+$commit_sha10 10th
+x notes on 10th commit
+
+$commit_sha9 9th
+
+$commit_sha8 8th
+z notes on 8th commit
+
+$commit_sha7 7th
+x notes on 7th commit
+
+$commit_sha6 6th
+
+$commit_sha5 5th
+z notes on 5th commit
+
+$commit_sha4 4th
+y notes on 4th commit
+
+$commit_sha3 3rd
+
+$commit_sha2 2nd
+z notes on 2nd commit
+
+$commit_sha1 1st
+
+EOF
+
+test_expect_success 'verify state of remote branch (z)' 'verify_notes z z'
+
+# At this point, before merging z into y, we have the following status:
+#
+# commit | base/x  | local/y | remote/z | diff from x to y/z         | result
+# -------|---------|---------|----------|----------------------------|-------
+# 1st    | [none]  | [none]  | [none]   | unchanged / unchanged      | [none]
+# 2nd    | [none]  | [none]  | 283b482  | unchanged / added          | 283b482
+# 3rd    | [none]  | 5772f42 | [none]   | added     / unchanged      | 5772f42
+# 4th    | [none]  | e2bfd06 | e2bfd06  | added     / added (same)   | e2bfd06
+# 5th    | [none]  | 154508c | 99fc34a  | added     / added (diff)   | ???
+# 6th    | 11d97fd | [none]  | [none]   | removed   / removed        | [none]
+# 7th    | 8970033 | [none]  | 8970033  | removed   / unchanged      | [none]
+# 8th    | a3daf8a | [none]  | 851e163  | removed   / changed        | ???
+# 9th    | 20c613c | 20c613c | [none]   | unchanged / removed        | [none]
+# 10th   | b8d03e1 | b8d03e1 | b8d03e1  | unchanged / unchanged      | b8d03e1
+# 11th   | 7abbc45 | 7abbc45 | 7e3c535  | unchanged / changed        | 7e3c535
+# 12th   | dd161bc | a66055f | [none]   | changed   / removed        | ???
+# 13th   | 5d30216 | 3a631fd | 5d30216  | changed   / unchanged      | 3a631fd
+# 14th   | b0c95b9 | 5de7ea7 | 5de7ea7  | changed   / changed (same) | 5de7ea7
+# 15th   | 457a85d | 68b8630 | 9b4b2c6  | changed   / changed (diff) | ???
+
+test_expect_success 'merge z into y with invalid strategy => Fail/No changes' '
+	git config core.notesRef refs/notes/y &&
+	test_must_fail git notes merge --strategy=foo z &&
+	# Verify no changes (y)
+	verify_notes y y
+'
+
+cat <<EOF | sort >expect_notes_ours
+68b8630d25516028bed862719855b3d6768d7833 $commit_sha15
+5de7ea7ad4f47e7ff91989fb82234634730f75df $commit_sha14
+3a631fdb6f41b05b55d8f4baf20728ba8f6fccbc $commit_sha13
+a66055fa82f7a03fe0c02a6aba3287a85abf7c62 $commit_sha12
+7e3c53503a3db8dd996cb62e37c66e070b44b54d $commit_sha11
+b8d03e173f67f6505a76f6e00cf93440200dd9be $commit_sha10
+154508c7a0bcad82b6fe4b472bc4c26b3bf0825b $commit_sha5
+e2bfd06a37dd2031684a59a6e2b033e212239c78 $commit_sha4
+5772f42408c0dd6f097a7ca2d24de0e78d1c46b1 $commit_sha3
+283b48219aee9a4105f6cab337e789065c82c2b9 $commit_sha2
+EOF
+
+cat >expect_log_ours <<EOF
+$commit_sha15 15th
+y notes on 15th commit
+
+$commit_sha14 14th
+y notes on 14th commit
+
+$commit_sha13 13th
+y notes on 13th commit
+
+$commit_sha12 12th
+y notes on 12th commit
+
+$commit_sha11 11th
+z notes on 11th commit
+
+$commit_sha10 10th
+x notes on 10th commit
+
+$commit_sha9 9th
+
+$commit_sha8 8th
+
+$commit_sha7 7th
+
+$commit_sha6 6th
+
+$commit_sha5 5th
+y notes on 5th commit
+
+$commit_sha4 4th
+y notes on 4th commit
+
+$commit_sha3 3rd
+y notes on 3rd commit
+
+$commit_sha2 2nd
+z notes on 2nd commit
+
+$commit_sha1 1st
+
+EOF
+
+test_expect_success 'merge z into y with "ours" strategy => Non-conflicting 3-way merge' '
+	git notes merge --strategy=ours z &&
+	verify_notes y ours
+'
+
+test_expect_success 'reset to pre-merge state (y)' '
+	git update-ref refs/notes/y refs/notes/y^1 &&
+	# Verify pre-merge state
+	verify_notes y y
+'
+
+cat <<EOF | sort >expect_notes_theirs
+9b4b2c61f0615412da3c10f98ff85b57c04ec765 $commit_sha15
+5de7ea7ad4f47e7ff91989fb82234634730f75df $commit_sha14
+3a631fdb6f41b05b55d8f4baf20728ba8f6fccbc $commit_sha13
+7e3c53503a3db8dd996cb62e37c66e070b44b54d $commit_sha11
+b8d03e173f67f6505a76f6e00cf93440200dd9be $commit_sha10
+851e1638784a884c7dd26c5d41f3340f6387413a $commit_sha8
+99fc34adfc400b95c67b013115e37e31aa9a6d23 $commit_sha5
+e2bfd06a37dd2031684a59a6e2b033e212239c78 $commit_sha4
+5772f42408c0dd6f097a7ca2d24de0e78d1c46b1 $commit_sha3
+283b48219aee9a4105f6cab337e789065c82c2b9 $commit_sha2
+EOF
+
+cat >expect_log_theirs <<EOF
+$commit_sha15 15th
+z notes on 15th commit
+
+$commit_sha14 14th
+y notes on 14th commit
+
+$commit_sha13 13th
+y notes on 13th commit
+
+$commit_sha12 12th
+
+$commit_sha11 11th
+z notes on 11th commit
+
+$commit_sha10 10th
+x notes on 10th commit
+
+$commit_sha9 9th
+
+$commit_sha8 8th
+z notes on 8th commit
+
+$commit_sha7 7th
+
+$commit_sha6 6th
+
+$commit_sha5 5th
+z notes on 5th commit
+
+$commit_sha4 4th
+y notes on 4th commit
+
+$commit_sha3 3rd
+y notes on 3rd commit
+
+$commit_sha2 2nd
+z notes on 2nd commit
+
+$commit_sha1 1st
+
+EOF
+
+test_expect_success 'merge z into y with "theirs" strategy => Non-conflicting 3-way merge' '
+	git notes merge --strategy=theirs z &&
+	verify_notes y theirs
+'
+
+test_expect_success 'reset to pre-merge state (y)' '
+	git update-ref refs/notes/y refs/notes/y^1 &&
+	# Verify pre-merge state
+	verify_notes y y
+'
+
+cat <<EOF | sort >expect_notes_union
+7c4e546efd0fe939f876beb262ece02797880b54 $commit_sha15
+5de7ea7ad4f47e7ff91989fb82234634730f75df $commit_sha14
+3a631fdb6f41b05b55d8f4baf20728ba8f6fccbc $commit_sha13
+a66055fa82f7a03fe0c02a6aba3287a85abf7c62 $commit_sha12
+7e3c53503a3db8dd996cb62e37c66e070b44b54d $commit_sha11
+b8d03e173f67f6505a76f6e00cf93440200dd9be $commit_sha10
+851e1638784a884c7dd26c5d41f3340f6387413a $commit_sha8
+6c841cc36ea496027290967ca96bd2bef54dbb47 $commit_sha5
+e2bfd06a37dd2031684a59a6e2b033e212239c78 $commit_sha4
+5772f42408c0dd6f097a7ca2d24de0e78d1c46b1 $commit_sha3
+283b48219aee9a4105f6cab337e789065c82c2b9 $commit_sha2
+EOF
+
+cat >expect_log_union <<EOF
+$commit_sha15 15th
+y notes on 15th commit
+
+z notes on 15th commit
+
+$commit_sha14 14th
+y notes on 14th commit
+
+$commit_sha13 13th
+y notes on 13th commit
+
+$commit_sha12 12th
+y notes on 12th commit
+
+$commit_sha11 11th
+z notes on 11th commit
+
+$commit_sha10 10th
+x notes on 10th commit
+
+$commit_sha9 9th
+
+$commit_sha8 8th
+z notes on 8th commit
+
+$commit_sha7 7th
+
+$commit_sha6 6th
+
+$commit_sha5 5th
+y notes on 5th commit
+
+z notes on 5th commit
+
+$commit_sha4 4th
+y notes on 4th commit
+
+$commit_sha3 3rd
+y notes on 3rd commit
+
+$commit_sha2 2nd
+z notes on 2nd commit
+
+$commit_sha1 1st
+
+EOF
+
+test_expect_success 'merge z into y with "union" strategy => Non-conflicting 3-way merge' '
+	git notes merge --strategy=union z &&
+	verify_notes y union
+'
+
+test_done
-- 
1.7.3.98.g5ad7d9

[PATCHv5 14/23] Documentation: Preliminary docs on 'git notes merge'

[Johan Herland]

This patch has been improved by the following contributions:
- Stephen Boyd: Use "automatically resolves" instead of "auto-resolves"
- Stephen Boyd: Remove unbalanced '('

Thanks-to: Stephen Boyd <bebarino@gmail.com>
Signed-off-by: Johan Herland <johan@herland.net>
---
 Documentation/git-notes.txt |   44 ++++++++++++++++++++++++++++++++++++++++++-
 1 files changed, 43 insertions(+), 1 deletions(-)

diff --git a/Documentation/git-notes.txt b/Documentation/git-notes.txt
index 2981d8c..07a5042 100644
--- a/Documentation/git-notes.txt
+++ b/Documentation/git-notes.txt
@@ -14,6 +14,7 @@ SYNOPSIS
 'git notes' append [-F <file> | -m <msg> | (-c | -C) <object>] [<object>]
 'git notes' edit [<object>]
 'git notes' show [<object>]
+'git notes' merge [-v | -q] [-s <strategy> ] <notes_ref>
 'git notes' remove [<object>]
 'git notes' prune [-n | -v]
 
@@ -83,6 +84,16 @@ edit::
 show::
 	Show the notes for a given object (defaults to HEAD).
 
+merge::
+	Merge the given notes ref into the current notes ref.
+	This will try to merge the changes made by the given
+	notes ref (called "remote") since the merge-base (if
+	any) into the current notes ref (called "local").
++
+If conflicts arise and a strategy for automatically resolving
+conflicting notes (see the -s/--strategy option) is not given,
+the merge fails (TODO).
+
 remove::
 	Remove the notes for a given object (defaults to HEAD).
 	This is equivalent to specifying an empty note message to
@@ -133,9 +144,23 @@ OPTIONS
 	Do not remove anything; just report the object names whose notes
 	would be removed.
 
+-s <strategy>::
+--strategy=<strategy>::
+	When merging notes, resolve notes conflicts using the given
+	strategy. The following strategies are recognized: "manual"
+	(default), "ours", "theirs" and "union".
+	See the "NOTES MERGE STRATEGIES" section below for more
+	information on each notes merge strategy.
+
+-q::
+--quiet::
+	When merging notes, operate quietly.
+
 -v::
 --verbose::
-	Report all object names whose notes are removed.
+	When merging notes, be more verbose.
+	When pruning notes, report all object names whose notes are
+	removed.
 
 
 DISCUSSION
@@ -163,6 +188,23 @@ object, in which case the history of the notes can be read with
 `git log -p -g <refname>`.
 
 
+NOTES MERGE STRATEGIES
+----------------------
+
+The default notes merge strategy is "manual", which is not yet
+implemented (TODO).
+
+"ours" automatically resolves conflicting notes in favor of the local
+version (i.e. the current notes ref).
+
+"theirs" automatically resolves notes conflicts in favor of the remote
+version (i.e. the given notes ref being merged into the current notes
+ref).
+
+"union" automatically resolves notes conflicts by concatenating the
+local and remote versions.
+
+
 EXAMPLES
 --------
 
-- 
1.7.3.98.g5ad7d9

[PATCHv5 15/23] git notes merge: Manual conflict resolution, part 1/2

[Johan Herland]

Conflicts (that are to be resolved manually) are written into a special-
purpose working tree, located at .git/NOTES_MERGE_WORKTREE. Within this
directory, conflicting notes entries are stored (with conflict markers
produced by ll_merge()) using the SHA1 of the annotated object. The
.git/NOTES_MERGE_WORKTREE directory will only contain the _conflicting_
note entries. The non-conflicting note entries (aka. the partial merge
result) are stored in 'local_tree', and the SHA1 of the resulting commit
is written to 'result_sha1'. The return value from notes_merge() is -1.

The user is told to edit the files within the .git/NOTES_MERGE_WORKTREE
directory in order to resolve the conflicts.

The patch also contains documentation and testcases for the correct setup
of .git/NOTES_MERGE_WORKTREE.

The next part will recombine the partial notes merge result with the
resolved conflicts in .git/NOTES_MERGE_WORKTREE to produce the complete
merge result.

This patch has been improved by the following contributions:
- Jonathan Nieder: Use trace_printf(...) instead of OUTPUT(o, 5, ...)

Thanks-to: Jonathan Nieder <jrnieder@gmail.com>
Signed-off-by: Johan Herland <johan@herland.net>
---
 Documentation/git-notes.txt           |   10 +-
 builtin/notes.c                       |    8 +-
 notes-merge.c                         |  166 ++++++++++++++++++-
 notes-merge.h                         |   11 +-
 t/t3310-notes-merge-manual-resolve.sh |  292 +++++++++++++++++++++++++++++++++
 5 files changed, 474 insertions(+), 13 deletions(-)
 create mode 100755 t/t3310-notes-merge-manual-resolve.sh

diff --git a/Documentation/git-notes.txt b/Documentation/git-notes.txt
index 07a5042..f003b7c 100644
--- a/Documentation/git-notes.txt
+++ b/Documentation/git-notes.txt
@@ -92,7 +92,9 @@ merge::
 +
 If conflicts arise and a strategy for automatically resolving
 conflicting notes (see the -s/--strategy option) is not given,
-the merge fails (TODO).
+the "manual" resolver is used. This resolver checks out the
+conflicting notes in a special worktree (`.git/NOTES_MERGE_WORKTREE`),
+and instructs the user to manually resolve the conflicts there.
 
 remove::
 	Remove the notes for a given object (defaults to HEAD).
@@ -191,8 +193,10 @@ object, in which case the history of the notes can be read with
 NOTES MERGE STRATEGIES
 ----------------------
 
-The default notes merge strategy is "manual", which is not yet
-implemented (TODO).
+The default notes merge strategy is "manual", which checks out
+conflicting notes in a special work tree for resolving notes conflicts
+(`.git/NOTES_MERGE_WORKTREE`), and instructs the user to resolve the
+conflicts in that work tree.
 
 "ours" automatically resolves conflicting notes in favor of the local
 version (i.e. the current notes ref).
diff --git a/builtin/notes.c b/builtin/notes.c
index a249f19..7a2a288 100644
--- a/builtin/notes.c
+++ b/builtin/notes.c
@@ -820,14 +820,14 @@ static int merge(int argc, const char **argv, const char *prefix)
 		/* Update default notes ref with new commit */
 		update_ref(msg.buf, default_notes_ref(), result_sha1, NULL,
 			   0, DIE_ON_ERR);
-	else
-		/* TODO: */
-		die("'git notes merge' cannot yet handle conflicts!");
+	else /* Merge has unresolved conflicts */
+		printf("Automatic notes merge failed. Fix conflicts in %s.\n",
+		       git_path(NOTES_MERGE_WORKTREE));
 
 	free_notes(t);
 	strbuf_release(&remote_ref);
 	strbuf_release(&msg);
-	return 0;
+	return result < 0; /* return non-zero on conflicts */
 }
 
 static int remove_cmd(int argc, const char **argv, const char *prefix)
diff --git a/notes-merge.c b/notes-merge.c
index f2fa12d..5734d0b 100644
--- a/notes-merge.c
+++ b/notes-merge.c
@@ -3,6 +3,9 @@
 #include "refs.h"
 #include "diff.h"
 #include "diffcore.h"
+#include "xdiff-interface.h"
+#include "ll-merge.h"
+#include "dir.h"
 #include "notes.h"
 #include "notes-merge.h"
 
@@ -263,16 +266,169 @@ static void diff_tree_local(struct notes_merge_options *o,
 	diff_tree_release_paths(&opt);
 }
 
+static void check_notes_merge_worktree(struct notes_merge_options *o)
+{
+	if (!o->has_worktree) {
+		/*
+		 * Must establish NOTES_MERGE_WORKTREE.
+		 * Abort if NOTES_MERGE_WORKTREE already exists
+		 */
+		if (file_exists(git_path(NOTES_MERGE_WORKTREE))) {
+			if (advice_resolve_conflict)
+				die("You have not concluded your previous "
+				    "notes merge (%s exists).\nPlease, use "
+				    "'git notes merge --commit' or 'git notes "
+				    "merge --reset' to commit/abort the "
+				    "previous merge before you start a new "
+				    "notes merge.", git_path("NOTES_MERGE_*"));
+			else
+				die("You have not concluded your notes merge "
+				    "(%s exists).", git_path("NOTES_MERGE_*"));
+		}
+
+		if (safe_create_leading_directories(git_path(
+				NOTES_MERGE_WORKTREE "/.test")))
+			die_errno("unable to create directory %s",
+				  git_path(NOTES_MERGE_WORKTREE));
+		o->has_worktree = 1;
+	} else if (!file_exists(git_path(NOTES_MERGE_WORKTREE)))
+		/* NOTES_MERGE_WORKTREE should already be established */
+		die("missing '%s'. This should not happen",
+		    git_path(NOTES_MERGE_WORKTREE));
+}
+
+static void write_buf_to_worktree(const unsigned char *obj,
+				  const char *buf, unsigned long size)
+{
+	int fd;
+	char *path = git_path(NOTES_MERGE_WORKTREE "/%s", sha1_to_hex(obj));
+	if (safe_create_leading_directories(path))
+		die_errno("unable to create directory for '%s'", path);
+	if (file_exists(path))
+		die("found existing file at '%s'", path);
+
+	fd = open(path, O_WRONLY | O_TRUNC | O_CREAT, 0666);
+	if (fd < 0)
+		die_errno("failed to open '%s'", path);
+
+	while (size > 0) {
+		long ret = write_in_full(fd, buf, size);
+		if (ret < 0) {
+			/* Ignore epipe */
+			if (errno == EPIPE)
+				break;
+			die_errno("notes-merge");
+		} else if (!ret) {
+			die("notes-merge: disk full?");
+		}
+		size -= ret;
+		buf += ret;
+	}
+
+	close(fd);
+}
+
+static void write_note_to_worktree(const unsigned char *obj,
+				   const unsigned char *note)
+{
+	enum object_type type;
+	unsigned long size;
+	void *buf = read_sha1_file(note, &type, &size);
+
+	if (!buf)
+		die("cannot read note %s for object %s",
+		    sha1_to_hex(note), sha1_to_hex(obj));
+	if (type != OBJ_BLOB)
+		die("blob expected in note %s for object %s",
+		    sha1_to_hex(note), sha1_to_hex(obj));
+	write_buf_to_worktree(obj, buf, size);
+	free(buf);
+}
+
+static int ll_merge_in_worktree(struct notes_merge_options *o,
+				struct notes_merge_pair *p)
+{
+	mmbuffer_t result_buf;
+	mmfile_t base, local, remote;
+	int status;
+
+	read_mmblob(&base, p->base);
+	read_mmblob(&local, p->local);
+	read_mmblob(&remote, p->remote);
+
+	status = ll_merge(&result_buf, sha1_to_hex(p->obj), &base, NULL,
+			  &local, o->local_ref, &remote, o->remote_ref, 0);
+
+	free(base.ptr);
+	free(local.ptr);
+	free(remote.ptr);
+
+	if ((status < 0) || !result_buf.ptr)
+		die("Failed to execute internal merge");
+
+	write_buf_to_worktree(p->obj, result_buf.ptr, result_buf.size);
+	free(result_buf.ptr);
+
+	return status;
+}
+
+static int merge_one_change_manual(struct notes_merge_options *o,
+				   struct notes_merge_pair *p,
+				   struct notes_tree *t)
+{
+	const char *lref = o->local_ref ? o->local_ref : "local version";
+	const char *rref = o->remote_ref ? o->remote_ref : "remote version";
+
+	trace_printf("\t\t\tmerge_one_change_manual(obj = %.7s, base = %.7s, "
+	       "local = %.7s, remote = %.7s)\n",
+	       sha1_to_hex(p->obj), sha1_to_hex(p->base),
+	       sha1_to_hex(p->local), sha1_to_hex(p->remote));
+
+	OUTPUT(o, 2, "Auto-merging notes for %s", sha1_to_hex(p->obj));
+	check_notes_merge_worktree(o);
+	if (is_null_sha1(p->local)) {
+		/* D/F conflict, checkout p->remote */
+		assert(!is_null_sha1(p->remote));
+		OUTPUT(o, 1, "CONFLICT (delete/modify): Notes for object %s "
+		       "deleted in %s and modified in %s. Version from %s "
+		       "left in tree.", sha1_to_hex(p->obj), lref, rref, rref);
+		write_note_to_worktree(p->obj, p->remote);
+	} else if (is_null_sha1(p->remote)) {
+		/* D/F conflict, checkout p->local */
+		assert(!is_null_sha1(p->local));
+		OUTPUT(o, 1, "CONFLICT (delete/modify): Notes for object %s "
+		       "deleted in %s and modified in %s. Version from %s "
+		       "left in tree.", sha1_to_hex(p->obj), rref, lref, lref);
+		write_note_to_worktree(p->obj, p->local);
+	} else {
+		/* "regular" conflict, checkout result of ll_merge() */
+		const char *reason = "content";
+		if (is_null_sha1(p->base))
+			reason = "add/add";
+		assert(!is_null_sha1(p->local));
+		assert(!is_null_sha1(p->remote));
+		OUTPUT(o, 1, "CONFLICT (%s): Merge conflict in notes for "
+		       "object %s", reason, sha1_to_hex(p->obj));
+		ll_merge_in_worktree(o, p);
+	}
+
+	trace_printf("\t\t\tremoving from partial merge result\n");
+	remove_note(t, p->obj);
+
+	return 1;
+}
+
 static int merge_one_change(struct notes_merge_options *o,
 			    struct notes_merge_pair *p, struct notes_tree *t)
 {
 	/*
-	 * Return 0 if change was resolved (and added to notes_tree),
-	 * 1 if conflict
+	 * Return 0 if change is successfully resolved (stored in notes_tree).
+	 * Return 1 is change results in a conflict (NOT stored in notes_tree,
+	 * but instead written to NOTES_MERGE_WORKTREE with conflict markers).
 	 */
 	switch (o->strategy) {
 	case NOTES_MERGE_RESOLVE_MANUAL:
-		return 1;
+		return merge_one_change_manual(o, p, t);
 	case NOTES_MERGE_RESOLVE_OURS:
 		OUTPUT(o, 2, "Using local notes for %s", sha1_to_hex(p->obj));
 		/* nothing to do */
@@ -478,8 +634,8 @@ int notes_merge(struct notes_merge_options *o,
 	result = merge_from_diffs(o, base_tree_sha1, local->tree->object.sha1,
 				  remote->tree->object.sha1, local_tree);
 
-	if (result > 0) { /* successful non-trivial merge */
-		/* Commit result */
+	if (result != 0) { /* non-trivial merge (with or without conflicts) */
+		/* Commit (partial) result */
 		struct commit_list *parents = NULL;
 		commit_list_insert(remote, &parents); /* LIFO order */
 		commit_list_insert(local, &parents);
diff --git a/notes-merge.h b/notes-merge.h
index ed356ae..55ef3d9 100644
--- a/notes-merge.h
+++ b/notes-merge.h
@@ -1,6 +1,8 @@
 #ifndef NOTES_MERGE_H
 #define NOTES_MERGE_H
 
+#define NOTES_MERGE_WORKTREE "NOTES_MERGE_WORKTREE"
+
 enum notes_merge_verbosity {
 	NOTES_MERGE_VERBOSITY_DEFAULT = 2,
 	NOTES_MERGE_VERBOSITY_MAX = 5
@@ -17,6 +19,7 @@ struct notes_merge_options {
 		NOTES_MERGE_RESOLVE_THEIRS,
 		NOTES_MERGE_RESOLVE_UNION
 	} strategy;
+	unsigned has_worktree:1;
 };
 
 void init_notes_merge_options(struct notes_merge_options *o);
@@ -51,7 +54,13 @@ void create_notes_commit(struct notes_tree *t, struct commit_list *parents,
  * 2. The merge successfully completes, producing a merge commit. local_tree
  *    contains the updated notes tree, the SHA1 of the resulting commit is
  *    written into 'result_sha1', and 1 is returned.
- * 3. The merge fails. result_sha1 is set to null_sha1, and -1 is returned.
+ * 3. The merge results in conflicts. This is similar to #2 in that the
+ *    partial merge result (i.e. merge result minus the unmerged entries)
+ *    are stored in 'local_tree', and the SHA1 or the resulting commit
+ *    (to be amended when the conflicts have been resolved) is written into
+ *    'result_sha1'. The unmerged entries are written into the
+ *    .git/NOTES_MERGE_WORKTREE directory with conflict markers.
+ *    -1 is returned.
  *
  * Both o->local_ref and o->remote_ref must be given (non-NULL), but either ref
  * (although not both) may refer to a non-existing notes ref, in which case
diff --git a/t/t3310-notes-merge-manual-resolve.sh b/t/t3310-notes-merge-manual-resolve.sh
new file mode 100755
index 0000000..eadb6b7
--- /dev/null
+++ b/t/t3310-notes-merge-manual-resolve.sh
@@ -0,0 +1,292 @@
+#!/bin/sh
+#
+# Copyright (c) 2010 Johan Herland
+#
+
+test_description='Test notes merging with manual conflict resolution'
+
+. ./test-lib.sh
+
+# Set up a notes merge scenario with different kinds of conflicts
+test_expect_success 'setup commits' '
+	test_commit 1st &&
+	test_commit 2nd &&
+	test_commit 3rd &&
+	test_commit 4th &&
+	test_commit 5th
+'
+
+commit_sha1=$(git rev-parse 1st^{commit})
+commit_sha2=$(git rev-parse 2nd^{commit})
+commit_sha3=$(git rev-parse 3rd^{commit})
+commit_sha4=$(git rev-parse 4th^{commit})
+commit_sha5=$(git rev-parse 5th^{commit})
+
+verify_notes () {
+	notes_ref="$1"
+	git -c core.notesRef="refs/notes/$notes_ref" notes |
+		sort >"output_notes_$notes_ref" &&
+	test_cmp "expect_notes_$notes_ref" "output_notes_$notes_ref" &&
+	git -c core.notesRef="refs/notes/$notes_ref" log --format="%H %s%n%N" \
+		>"output_log_$notes_ref" &&
+	test_cmp "expect_log_$notes_ref" "output_log_$notes_ref"
+}
+
+cat <<EOF | sort >expect_notes_x
+6e8e3febca3c2bb896704335cc4d0c34cb2f8715 $commit_sha4
+e5388c10860456ee60673025345fe2e153eb8cf8 $commit_sha3
+ceefa674873670e7ecd131814d909723cce2b669 $commit_sha2
+EOF
+
+cat >expect_log_x <<EOF
+$commit_sha5 5th
+
+$commit_sha4 4th
+x notes on 4th commit
+
+$commit_sha3 3rd
+x notes on 3rd commit
+
+$commit_sha2 2nd
+x notes on 2nd commit
+
+$commit_sha1 1st
+
+EOF
+
+test_expect_success 'setup merge base (x)' '
+	git config core.notesRef refs/notes/x &&
+	git notes add -m "x notes on 2nd commit" 2nd &&
+	git notes add -m "x notes on 3rd commit" 3rd &&
+	git notes add -m "x notes on 4th commit" 4th &&
+	verify_notes x
+'
+
+cat <<EOF | sort >expect_notes_y
+e2bfd06a37dd2031684a59a6e2b033e212239c78 $commit_sha4
+5772f42408c0dd6f097a7ca2d24de0e78d1c46b1 $commit_sha3
+b0a6021ec006d07e80e9b20ec9b444cbd9d560d3 $commit_sha1
+EOF
+
+cat >expect_log_y <<EOF
+$commit_sha5 5th
+
+$commit_sha4 4th
+y notes on 4th commit
+
+$commit_sha3 3rd
+y notes on 3rd commit
+
+$commit_sha2 2nd
+
+$commit_sha1 1st
+y notes on 1st commit
+
+EOF
+
+test_expect_success 'setup local branch (y)' '
+	git update-ref refs/notes/y refs/notes/x &&
+	git config core.notesRef refs/notes/y &&
+	git notes add -f -m "y notes on 1st commit" 1st &&
+	git notes remove 2nd &&
+	git notes add -f -m "y notes on 3rd commit" 3rd &&
+	git notes add -f -m "y notes on 4th commit" 4th &&
+	verify_notes y
+'
+
+cat <<EOF | sort >expect_notes_z
+cff59c793c20bb49a4e01bc06fb06bad642e0d54 $commit_sha4
+283b48219aee9a4105f6cab337e789065c82c2b9 $commit_sha2
+0a81da8956346e19bcb27a906f04af327e03e31b $commit_sha1
+EOF
+
+cat >expect_log_z <<EOF
+$commit_sha5 5th
+
+$commit_sha4 4th
+z notes on 4th commit
+
+$commit_sha3 3rd
+
+$commit_sha2 2nd
+z notes on 2nd commit
+
+$commit_sha1 1st
+z notes on 1st commit
+
+EOF
+
+test_expect_success 'setup remote branch (z)' '
+	git update-ref refs/notes/z refs/notes/x &&
+	git config core.notesRef refs/notes/z &&
+	git notes add -f -m "z notes on 1st commit" 1st &&
+	git notes add -f -m "z notes on 2nd commit" 2nd &&
+	git notes remove 3rd &&
+	git notes add -f -m "z notes on 4th commit" 4th &&
+	verify_notes z
+'
+
+# At this point, before merging z into y, we have the following status:
+#
+# commit | base/x  | local/y | remote/z | diff from x to y/z
+# -------|---------|---------|----------|---------------------------
+# 1st    | [none]  | b0a6021 | 0a81da8  | added     / added (diff)
+# 2nd    | ceefa67 | [none]  | 283b482  | removed   / changed
+# 3rd    | e5388c1 | 5772f42 | [none]   | changed   / removed
+# 4th    | 6e8e3fe | e2bfd06 | cff59c7  | changed   / changed (diff)
+# 5th    | [none]  | [none]  | [none]   | [none]
+
+cat <<EOF | sort >expect_conflicts
+$commit_sha1
+$commit_sha2
+$commit_sha3
+$commit_sha4
+EOF
+
+cat >expect_conflict_$commit_sha1 <<EOF
+<<<<<<< refs/notes/m
+y notes on 1st commit
+=======
+z notes on 1st commit
+>>>>>>> refs/notes/z
+EOF
+
+cat >expect_conflict_$commit_sha2 <<EOF
+z notes on 2nd commit
+EOF
+
+cat >expect_conflict_$commit_sha3 <<EOF
+y notes on 3rd commit
+EOF
+
+cat >expect_conflict_$commit_sha4 <<EOF
+<<<<<<< refs/notes/m
+y notes on 4th commit
+=======
+z notes on 4th commit
+>>>>>>> refs/notes/z
+EOF
+
+cp expect_notes_y expect_notes_m
+cp expect_log_y expect_log_m
+
+git rev-parse refs/notes/y > pre_merge_y
+
+test_expect_success 'merge z into m (== y) with default ("manual") resolver => Conflicting 3-way merge' '
+	git update-ref refs/notes/m refs/notes/y &&
+	git config core.notesRef refs/notes/m &&
+	test_must_fail git notes merge z >output &&
+	# Output should point to where to resolve conflicts
+	grep -q "\\.git/NOTES_MERGE_WORKTREE" output &&
+	# Inspect merge conflicts
+	ls .git/NOTES_MERGE_WORKTREE >output_conflicts &&
+	test_cmp expect_conflicts output_conflicts &&
+	( for f in $(cat expect_conflicts); do
+		test_cmp "expect_conflict_$f" ".git/NOTES_MERGE_WORKTREE/$f" ||
+		exit 1
+	done ) &&
+	# Verify that current notes tree (pre-merge) has not changed (m == y)
+	verify_notes y &&
+	verify_notes m &&
+	test "$(git rev-parse refs/notes/m)" = "$(cat pre_merge_y)"
+'
+
+cat <<EOF | sort >expect_notes_z
+00494adecf2d9635a02fa431308d67993f853968 $commit_sha4
+283b48219aee9a4105f6cab337e789065c82c2b9 $commit_sha2
+0a81da8956346e19bcb27a906f04af327e03e31b $commit_sha1
+EOF
+
+cat >expect_log_z <<EOF
+$commit_sha5 5th
+
+$commit_sha4 4th
+z notes on 4th commit
+
+More z notes on 4th commit
+
+$commit_sha3 3rd
+
+$commit_sha2 2nd
+z notes on 2nd commit
+
+$commit_sha1 1st
+z notes on 1st commit
+
+EOF
+
+test_expect_success 'change notes in z' '
+	git notes --ref z append -m "More z notes on 4th commit" 4th &&
+	verify_notes z
+'
+
+test_expect_success 'cannot do merge w/conflicts when previous merge is unfinished' '
+	test -d .git/NOTES_MERGE_WORKTREE &&
+	test_must_fail git notes merge z >output 2>&1 &&
+	# Output should indicate what is wrong
+	grep -q "\\.git/NOTES_MERGE_\\* exists" output
+'
+
+# Setup non-conflicting merge between x and new notes ref w
+
+cat <<EOF | sort >expect_notes_w
+ceefa674873670e7ecd131814d909723cce2b669 $commit_sha2
+f75d1df88cbfe4258d49852f26cfc83f2ad4494b $commit_sha1
+EOF
+
+cat >expect_log_w <<EOF
+$commit_sha5 5th
+
+$commit_sha4 4th
+
+$commit_sha3 3rd
+
+$commit_sha2 2nd
+x notes on 2nd commit
+
+$commit_sha1 1st
+w notes on 1st commit
+
+EOF
+
+test_expect_success 'setup unrelated notes ref (w)' '
+	git config core.notesRef refs/notes/w &&
+	git notes add -m "w notes on 1st commit" 1st &&
+	git notes add -m "x notes on 2nd commit" 2nd &&
+	verify_notes w
+'
+
+cat <<EOF | sort >expect_notes_w
+6e8e3febca3c2bb896704335cc4d0c34cb2f8715 $commit_sha4
+e5388c10860456ee60673025345fe2e153eb8cf8 $commit_sha3
+ceefa674873670e7ecd131814d909723cce2b669 $commit_sha2
+f75d1df88cbfe4258d49852f26cfc83f2ad4494b $commit_sha1
+EOF
+
+cat >expect_log_w <<EOF
+$commit_sha5 5th
+
+$commit_sha4 4th
+x notes on 4th commit
+
+$commit_sha3 3rd
+x notes on 3rd commit
+
+$commit_sha2 2nd
+x notes on 2nd commit
+
+$commit_sha1 1st
+w notes on 1st commit
+
+EOF
+
+test_expect_success 'can do merge without conflicts even if previous merge is unfinished (x => w)' '
+	test -d .git/NOTES_MERGE_WORKTREE &&
+	git notes merge x &&
+	verify_notes w &&
+	# Verify that other notes refs has not changed (x and y)
+	verify_notes x &&
+	verify_notes y
+'
+
+test_done
-- 
1.7.3.98.g5ad7d9

[PATCHv5 16/23] git notes merge: Manual conflict resolution, part 2/2

[Johan Herland]

When the notes merge conflicts in .git/NOTES_MERGE_WORKTREE have been
resolved, we need to record a new notes commit on the appropriate notes
ref with the resolved notes.

This patch implements 'git notes merge --commit' which the user should
run after resolving conflicts in the notes merge worktree. This command
finalizes the notes merge by recombining the partial notes tree from
part 1 with the now-resolved conflicts in the notes merge worktree in a
merge commit, and updating the appropriate ref to this merge commit.

In order to correctly finalize the merge, we need to keep track of three
things:

- The partial merge result from part 1, containing the auto-merged notes.
  This is now stored into a ref called .git/NOTES_MERGE_PARTIAL.
- The unmerged notes. These are already stored in
  .git/NOTES_MERGE_WORKTREE, thanks to part 1.
- The notes ref to be updated by the finalized merge result. This is now
  stored in a symref called .git/NOTES_MERGE_REF.

In addition to "git notes merge --commit", which uses the above details
to create the finalized notes merge commit, this patch also implements
"git notes merge --reset", which aborts the ongoing notes merge by simply
removing the files/directory described above.

FTR, "git notes merge --commit" reuses "git notes merge --reset" to remove
the information described above (.git/NOTES_MERGE_*) after the notes merge
have been successfully finalized.

The patch also contains documentation and testcases for the two new options.

This patch has been improved by the following contributions:
- Ævar Arnfjörð Bjarmason: Fix nonsense sentence in --commit description
- Sverre Rabbelier: Rename --reset to --abort

Thanks-to: Ævar Arnfjörð Bjarmason <avarab@gmail.com>
Thanks-to: Sverre Rabbelier <srabbelier@gmail.com>
Signed-off-by: Johan Herland <johan@herland.net>
---
 Documentation/git-notes.txt           |   22 ++++
 builtin/notes.c                       |  106 +++++++++++++++++++-
 notes-merge.c                         |   71 +++++++++++++-
 notes-merge.h                         |   23 +++++
 t/t3310-notes-merge-manual-resolve.sh |  176 +++++++++++++++++++++++++++++++++
 5 files changed, 394 insertions(+), 4 deletions(-)

diff --git a/Documentation/git-notes.txt b/Documentation/git-notes.txt
index f003b7c..a822551 100644
--- a/Documentation/git-notes.txt
+++ b/Documentation/git-notes.txt
@@ -15,6 +15,8 @@ SYNOPSIS
 'git notes' edit [<object>]
 'git notes' show [<object>]
 'git notes' merge [-v | -q] [-s <strategy> ] <notes_ref>
+'git notes' merge --commit [-v | -q]
+'git notes' merge --abort [-v | -q]
 'git notes' remove [<object>]
 'git notes' prune [-n | -v]
 
@@ -95,6 +97,9 @@ conflicting notes (see the -s/--strategy option) is not given,
 the "manual" resolver is used. This resolver checks out the
 conflicting notes in a special worktree (`.git/NOTES_MERGE_WORKTREE`),
 and instructs the user to manually resolve the conflicts there.
+When done, the user can either finalize the merge with
+'git notes merge --commit', or abort the merge with
+'git notes merge --abort'.
 
 remove::
 	Remove the notes for a given object (defaults to HEAD).
@@ -154,6 +159,20 @@ OPTIONS
 	See the "NOTES MERGE STRATEGIES" section below for more
 	information on each notes merge strategy.
 
+--commit::
+	Finalize an in-progress 'git notes merge'. Use this option
+	when you have resolved the conflicts that 'git notes merge'
+	stored in .git/NOTES_MERGE_WORKTREE. This amends the partial
+	merge commit created by 'git notes merge' (stored in
+	.git/NOTES_MERGE_PARTIAL) by adding the notes in
+	.git/NOTES_MERGE_WORKTREE. The notes ref stored in the
+	.git/NOTES_MERGE_REF symref is updated to the resulting commit.
+
+--abort::
+	Abort/reset a in-progress 'git notes merge', i.e. a notes merge
+	with conflicts. This simply removes all files related to the
+	notes merge.
+
 -q::
 --quiet::
 	When merging notes, operate quietly.
@@ -197,6 +216,9 @@ The default notes merge strategy is "manual", which checks out
 conflicting notes in a special work tree for resolving notes conflicts
 (`.git/NOTES_MERGE_WORKTREE`), and instructs the user to resolve the
 conflicts in that work tree.
+When done, the user can either finalize the merge with
+'git notes merge --commit', or abort the merge with
+'git notes merge --abort'.
 
 "ours" automatically resolves conflicting notes in favor of the local
 version (i.e. the current notes ref).
diff --git a/builtin/notes.c b/builtin/notes.c
index 7a2a288..db60ead 100644
--- a/builtin/notes.c
+++ b/builtin/notes.c
@@ -27,6 +27,8 @@ static const char * const git_notes_usage[] = {
 	"git notes [--ref <notes_ref>] edit [<object>]",
 	"git notes [--ref <notes_ref>] show [<object>]",
 	"git notes [--ref <notes_ref>] merge [-v | -q] [-s <strategy> ] <notes_ref>",
+	"git notes merge --commit [-v | -q]",
+	"git notes merge --abort [-v | -q]",
 	"git notes [--ref <notes_ref>] remove [<object>]",
 	"git notes [--ref <notes_ref>] prune [-n | -v]",
 	NULL
@@ -65,6 +67,8 @@ static const char * const git_notes_show_usage[] = {
 
 static const char * const git_notes_merge_usage[] = {
 	"git notes merge [<options>] <notes_ref>",
+	"git notes merge --commit [<options>]",
+	"git notes merge --abort [<options>]",
 	NULL
 };
 
@@ -761,33 +765,119 @@ static int show(int argc, const char **argv, const char *prefix)
 	return retval;
 }
 
+static int merge_abort(struct notes_merge_options *o)
+{
+	int ret = 0;
+
+	/*
+	 * Remove .git/NOTES_MERGE_PARTIAL and .git/NOTES_MERGE_REF, and call
+	 * notes_merge_abort() to remove .git/NOTES_MERGE_WORKTREE.
+	 */
+
+	if (delete_ref("NOTES_MERGE_PARTIAL", NULL, 0))
+		ret += error("Failed to delete ref NOTES_MERGE_PARTIAL");
+	if (delete_ref("NOTES_MERGE_REF", NULL, REF_NODEREF))
+		ret += error("Failed to delete ref NOTES_MERGE_REF");
+	if (notes_merge_abort(o))
+		ret += error("Failed to remove 'git notes merge' worktree");
+	return ret;
+}
+
+static int merge_commit(struct notes_merge_options *o)
+{
+	struct strbuf msg = STRBUF_INIT;
+	unsigned char sha1[20];
+	struct notes_tree *t;
+	struct commit *partial;
+	struct pretty_print_context pretty_ctx;
+
+	/*
+	 * Read partial merge result from .git/NOTES_MERGE_PARTIAL,
+	 * and target notes ref from .git/NOTES_MERGE_REF.
+	 */
+
+	if (get_sha1("NOTES_MERGE_PARTIAL", sha1))
+		die("Failed to read ref NOTES_MERGE_PARTIAL");
+	else if (!(partial = lookup_commit_reference(sha1)))
+		die("Could not find commit from NOTES_MERGE_PARTIAL.");
+	else if (parse_commit(partial))
+		die("Could not parse commit from NOTES_MERGE_PARTIAL.");
+
+	t = xcalloc(1, sizeof(struct notes_tree));
+	init_notes(t, "NOTES_MERGE_PARTIAL", combine_notes_overwrite, 0);
+
+	o->local_ref = resolve_ref("NOTES_MERGE_REF", sha1, 0, 0);
+	if (!o->local_ref)
+		die("Failed to resolve NOTES_MERGE_REF");
+
+	if (notes_merge_commit(o, t, partial, sha1))
+		die("Failed to finalize notes merge");
+
+	/* Reuse existing commit message in reflog message */
+	memset(&pretty_ctx, 0, sizeof(pretty_ctx));
+	format_commit_message(partial, "%s", &msg, &pretty_ctx);
+	strbuf_trim(&msg);
+	strbuf_insert(&msg, 0, "notes: ", 7);
+	update_ref(msg.buf, o->local_ref, sha1, NULL, 0, DIE_ON_ERR);
+
+	free_notes(t);
+	strbuf_release(&msg);
+	return merge_abort(o);
+}
+
 static int merge(int argc, const char **argv, const char *prefix)
 {
 	struct strbuf remote_ref = STRBUF_INIT, msg = STRBUF_INIT;
 	unsigned char result_sha1[20];
 	struct notes_tree *t;
 	struct notes_merge_options o;
+	int do_merge = 0, do_commit = 0, do_abort = 0;
 	int verbosity = 0, result;
 	const char *strategy = NULL;
 	struct option options[] = {
+		OPT_GROUP("General options"),
 		OPT__VERBOSITY(&verbosity),
+		OPT_GROUP("Merge options"),
 		OPT_STRING('s', "strategy", &strategy, "strategy",
 			   "resolve notes conflicts using the given "
 			   "strategy (manual/ours/theirs/union)"),
+		OPT_GROUP("Committing unmerged notes"),
+		{ OPTION_BOOLEAN, 0, "commit", &do_commit, NULL,
+			"finalize notes merge by committing unmerged notes",
+			PARSE_OPT_NOARG | PARSE_OPT_NONEG },
+		OPT_GROUP("Aborting notes merge resolution"),
+		{ OPTION_BOOLEAN, 0, "abort", &do_abort, NULL,
+			"abort notes merge",
+			PARSE_OPT_NOARG | PARSE_OPT_NONEG },
 		OPT_END()
 	};
 
 	argc = parse_options(argc, argv, prefix, options,
 			     git_notes_merge_usage, 0);
 
-	if (argc != 1) {
+	if (strategy || do_commit + do_abort == 0)
+		do_merge = 1;
+	if (do_merge + do_commit + do_abort != 1) {
+		error("cannot mix --commit, --abort or -s/--strategy");
+		usage_with_options(git_notes_merge_usage, options);
+	}
+
+	if (do_merge && argc != 1) {
 		error("Must specify a notes ref to merge");
 		usage_with_options(git_notes_merge_usage, options);
+	} else if (!do_merge && argc) {
+		error("too many parameters");
+		usage_with_options(git_notes_merge_usage, options);
 	}
 
 	init_notes_merge_options(&o);
 	o.verbosity = verbosity + NOTES_MERGE_VERBOSITY_DEFAULT;
 
+	if (do_abort)
+		return merge_abort(&o);
+	if (do_commit)
+		return merge_commit(&o);
+
 	o.local_ref = default_notes_ref();
 	strbuf_addstr(&remote_ref, argv[0]);
 	expand_notes_ref(&remote_ref);
@@ -820,9 +910,19 @@ static int merge(int argc, const char **argv, const char *prefix)
 		/* Update default notes ref with new commit */
 		update_ref(msg.buf, default_notes_ref(), result_sha1, NULL,
 			   0, DIE_ON_ERR);
-	else /* Merge has unresolved conflicts */
-		printf("Automatic notes merge failed. Fix conflicts in %s.\n",
+	else { /* Merge has unresolved conflicts */
+		/* Update .git/NOTES_MERGE_PARTIAL with partial merge result */
+		update_ref(msg.buf, "NOTES_MERGE_PARTIAL", result_sha1, NULL,
+			   0, DIE_ON_ERR);
+		/* Store ref-to-be-updated into .git/NOTES_MERGE_REF */
+		if (create_symref("NOTES_MERGE_REF", default_notes_ref(), NULL))
+			die("Failed to store link to current notes ref (%s)",
+			    default_notes_ref());
+		printf("Automatic notes merge failed. Fix conflicts in %s and "
+		       "commit the result with 'git notes merge --commit', or "
+		       "abort the merge with 'git notes merge --abort'.\n",
 		       git_path(NOTES_MERGE_WORKTREE));
+	}
 
 	free_notes(t);
 	strbuf_release(&remote_ref);
diff --git a/notes-merge.c b/notes-merge.c
index 5734d0b..b44273c 100644
--- a/notes-merge.c
+++ b/notes-merge.c
@@ -278,7 +278,7 @@ static void check_notes_merge_worktree(struct notes_merge_options *o)
 				die("You have not concluded your previous "
 				    "notes merge (%s exists).\nPlease, use "
 				    "'git notes merge --commit' or 'git notes "
-				    "merge --reset' to commit/abort the "
+				    "merge --abort' to commit/abort the "
 				    "previous merge before you start a new "
 				    "notes merge.", git_path("NOTES_MERGE_*"));
 			else
@@ -649,3 +649,72 @@ found_result:
 	       result, sha1_to_hex(result_sha1));
 	return result;
 }
+
+int notes_merge_commit(struct notes_merge_options *o,
+		       struct notes_tree *partial_tree,
+		       struct commit *partial_commit,
+		       unsigned char *result_sha1)
+{
+	/*
+	 * Iterate through files in .git/NOTES_MERGE_WORKTREE and add all
+	 * found notes to 'partial_tree'. Write the updates notes tree to
+	 * the DB, and commit the resulting tree object while reusing the
+	 * commit message and parents from 'partial_commit'.
+	 * Finally store the new commit object SHA1 into 'result_sha1'.
+	 */
+	struct dir_struct dir;
+	const char *path = git_path(NOTES_MERGE_WORKTREE "/");
+	int path_len = strlen(path), i;
+	const char *msg = strstr(partial_commit->buffer, "\n\n");
+
+	OUTPUT(o, 3, "Committing notes in notes merge worktree at %.*s",
+	       path_len - 1, path);
+
+	if (!msg || msg[2] == '\0')
+		die("partial notes commit has empty message");
+	msg += 2;
+
+	memset(&dir, 0, sizeof(dir));
+	read_directory(&dir, path, path_len, NULL);
+	for (i = 0; i < dir.nr; i++) {
+		struct dir_entry *ent = dir.entries[i];
+		struct stat st;
+		const char *relpath = ent->name + path_len;
+		unsigned char obj_sha1[20], blob_sha1[20];
+
+		if (ent->len - path_len != 40 || get_sha1_hex(relpath, obj_sha1)) {
+			OUTPUT(o, 3, "Skipping non-SHA1 entry '%s'", ent->name);
+			continue;
+		}
+
+		/* write file as blob, and add to partial_tree */
+		if (stat(ent->name, &st))
+			die_errno("Failed to stat '%s'", ent->name);
+		if (index_path(blob_sha1, ent->name, &st, 1))
+			die("Failed to write blob object from '%s'", ent->name);
+		if (add_note(partial_tree, obj_sha1, blob_sha1, NULL))
+			die("Failed to add resolved note '%s' to notes tree",
+			    ent->name);
+		OUTPUT(o, 4, "Added resolved note for object %s: %s",
+		       sha1_to_hex(obj_sha1), sha1_to_hex(blob_sha1));
+	}
+
+	create_notes_commit(partial_tree, partial_commit->parents, msg,
+			    result_sha1);
+	OUTPUT(o, 4, "Finalized notes merge commit: %s",
+	       sha1_to_hex(result_sha1));
+	return 0;
+}
+
+int notes_merge_abort(struct notes_merge_options *o)
+{
+	/* Remove .git/NOTES_MERGE_WORKTREE directory and all files within */
+	struct strbuf buf = STRBUF_INIT;
+	int ret;
+
+	strbuf_addstr(&buf, git_path(NOTES_MERGE_WORKTREE));
+	OUTPUT(o, 3, "Removing notes merge worktree at %s", buf.buf);
+	ret = remove_dir_recursively(&buf, 0);
+	strbuf_release(&buf);
+	return ret;
+}
diff --git a/notes-merge.h b/notes-merge.h
index 55ef3d9..aa75693 100644
--- a/notes-merge.h
+++ b/notes-merge.h
@@ -71,4 +71,27 @@ int notes_merge(struct notes_merge_options *o,
 		struct notes_tree *local_tree,
 		unsigned char *result_sha1);
 
+/*
+ * Finalize conflict resolution from an earlier notes_merge()
+ *
+ * The given notes tree 'partial_tree' must be the notes_tree corresponding to
+ * the given 'partial_commit', the partial result commit created by a previous
+ * call to notes_merge().
+ *
+ * This function will add the (now resolved) notes in .git/NOTES_MERGE_WORKTREE
+ * to 'partial_tree', and create a final notes merge commit, the SHA1 of which
+ * will be stored in 'result_sha1'.
+ */
+int notes_merge_commit(struct notes_merge_options *o,
+		       struct notes_tree *partial_tree,
+		       struct commit *partial_commit,
+		       unsigned char *result_sha1);
+
+/*
+ * Abort conflict resolution from an earlier notes_merge()
+ *
+ * Removes the notes merge worktree in .git/NOTES_MERGE_WORKTREE.
+ */
+int notes_merge_abort(struct notes_merge_options *o);
+
 #endif
diff --git a/t/t3310-notes-merge-manual-resolve.sh b/t/t3310-notes-merge-manual-resolve.sh
index eadb6b7..0ec315a 100755
--- a/t/t3310-notes-merge-manual-resolve.sh
+++ b/t/t3310-notes-merge-manual-resolve.sh
@@ -171,6 +171,7 @@ cp expect_notes_y expect_notes_m
 cp expect_log_y expect_log_m
 
 git rev-parse refs/notes/y > pre_merge_y
+git rev-parse refs/notes/z > pre_merge_z
 
 test_expect_success 'merge z into m (== y) with default ("manual") resolver => Conflicting 3-way merge' '
 	git update-ref refs/notes/m refs/notes/y &&
@@ -289,4 +290,179 @@ test_expect_success 'can do merge without conflicts even if previous merge is un
 	verify_notes y
 '
 
+cat <<EOF | sort >expect_notes_m
+021faa20e931fb48986ffc6282b4bb05553ac946 $commit_sha4
+5772f42408c0dd6f097a7ca2d24de0e78d1c46b1 $commit_sha3
+283b48219aee9a4105f6cab337e789065c82c2b9 $commit_sha2
+0a59e787e6d688aa6309e56e8c1b89431a0fc1c1 $commit_sha1
+EOF
+
+cat >expect_log_m <<EOF
+$commit_sha5 5th
+
+$commit_sha4 4th
+y and z notes on 4th commit
+
+$commit_sha3 3rd
+y notes on 3rd commit
+
+$commit_sha2 2nd
+z notes on 2nd commit
+
+$commit_sha1 1st
+y and z notes on 1st commit
+
+EOF
+
+test_expect_success 'finalize conflicting merge (z => m)' '
+	# Resolve conflicts and finalize merge
+	cat >.git/NOTES_MERGE_WORKTREE/$commit_sha1 <<EOF &&
+y and z notes on 1st commit
+EOF
+	cat >.git/NOTES_MERGE_WORKTREE/$commit_sha4 <<EOF &&
+y and z notes on 4th commit
+EOF
+	git notes merge --commit &&
+	# No .git/NOTES_MERGE_* files left
+	test_must_fail ls .git/NOTES_MERGE_* >output 2>/dev/null &&
+	test_cmp /dev/null output &&
+	# Merge commit has pre-merge y and pre-merge z as parents
+	test "$(git rev-parse refs/notes/m^1)" = "$(cat pre_merge_y)" &&
+	test "$(git rev-parse refs/notes/m^2)" = "$(cat pre_merge_z)" &&
+	# Merge commit mentions the notes refs merged
+	git log -1 --format=%B refs/notes/m > merge_commit_msg &&
+	grep -q refs/notes/m merge_commit_msg &&
+	grep -q refs/notes/z merge_commit_msg &&
+	# Verify contents of merge result
+	verify_notes m &&
+	# Verify that other notes refs has not changed (w, x, y and z)
+	verify_notes w &&
+	verify_notes x &&
+	verify_notes y &&
+	verify_notes z
+'
+
+cat >expect_conflict_$commit_sha4 <<EOF
+<<<<<<< refs/notes/m
+y notes on 4th commit
+=======
+z notes on 4th commit
+
+More z notes on 4th commit
+>>>>>>> refs/notes/z
+EOF
+
+cp expect_notes_y expect_notes_m
+cp expect_log_y expect_log_m
+
+git rev-parse refs/notes/y > pre_merge_y
+git rev-parse refs/notes/z > pre_merge_z
+
+test_expect_success 'redo merge of z into m (== y) with default ("manual") resolver => Conflicting 3-way merge' '
+	git update-ref refs/notes/m refs/notes/y &&
+	git config core.notesRef refs/notes/m &&
+	test_must_fail git notes merge z >output &&
+	# Output should point to where to resolve conflicts
+	grep -q "\\.git/NOTES_MERGE_WORKTREE" output &&
+	# Inspect merge conflicts
+	ls .git/NOTES_MERGE_WORKTREE >output_conflicts &&
+	test_cmp expect_conflicts output_conflicts &&
+	( for f in $(cat expect_conflicts); do
+		test_cmp "expect_conflict_$f" ".git/NOTES_MERGE_WORKTREE/$f" ||
+		exit 1
+	done ) &&
+	# Verify that current notes tree (pre-merge) has not changed (m == y)
+	verify_notes y &&
+	verify_notes m &&
+	test "$(git rev-parse refs/notes/m)" = "$(cat pre_merge_y)"
+'
+
+test_expect_success 'abort notes merge' '
+	git notes merge --abort &&
+	# No .git/NOTES_MERGE_* files left
+	test_must_fail ls .git/NOTES_MERGE_* >output 2>/dev/null &&
+	test_cmp /dev/null output &&
+	# m has not moved (still == y)
+	test "$(git rev-parse refs/notes/m)" = "$(cat pre_merge_y)"
+	# Verify that other notes refs has not changed (w, x, y and z)
+	verify_notes w &&
+	verify_notes x &&
+	verify_notes y &&
+	verify_notes z
+'
+
+git rev-parse refs/notes/y > pre_merge_y
+git rev-parse refs/notes/z > pre_merge_z
+
+test_expect_success 'redo merge of z into m (== y) with default ("manual") resolver => Conflicting 3-way merge' '
+	test_must_fail git notes merge z >output &&
+	# Output should point to where to resolve conflicts
+	grep -q "\\.git/NOTES_MERGE_WORKTREE" output &&
+	# Inspect merge conflicts
+	ls .git/NOTES_MERGE_WORKTREE >output_conflicts &&
+	test_cmp expect_conflicts output_conflicts &&
+	( for f in $(cat expect_conflicts); do
+		test_cmp "expect_conflict_$f" ".git/NOTES_MERGE_WORKTREE/$f" ||
+		exit 1
+	done ) &&
+	# Verify that current notes tree (pre-merge) has not changed (m == y)
+	verify_notes y &&
+	verify_notes m &&
+	test "$(git rev-parse refs/notes/m)" = "$(cat pre_merge_y)"
+'
+
+cat <<EOF | sort >expect_notes_m
+304dfb4325cf243025b9957486eb605a9b51c199 $commit_sha5
+283b48219aee9a4105f6cab337e789065c82c2b9 $commit_sha2
+0a59e787e6d688aa6309e56e8c1b89431a0fc1c1 $commit_sha1
+EOF
+
+cat >expect_log_m <<EOF
+$commit_sha5 5th
+new note on 5th commit
+
+$commit_sha4 4th
+
+$commit_sha3 3rd
+
+$commit_sha2 2nd
+z notes on 2nd commit
+
+$commit_sha1 1st
+y and z notes on 1st commit
+
+EOF
+
+test_expect_success 'add + remove notes in finalized merge (z => m)' '
+	# Resolve one conflict
+	cat >.git/NOTES_MERGE_WORKTREE/$commit_sha1 <<EOF &&
+y and z notes on 1st commit
+EOF
+	# Remove another conflict
+	rm .git/NOTES_MERGE_WORKTREE/$commit_sha4 &&
+	# Remove a D/F conflict
+	rm .git/NOTES_MERGE_WORKTREE/$commit_sha3 &&
+	# Add a new note
+	echo "new note on 5th commit" > .git/NOTES_MERGE_WORKTREE/$commit_sha5 &&
+	# Finalize merge
+	git notes merge --commit &&
+	# No .git/NOTES_MERGE_* files left
+	test_must_fail ls .git/NOTES_MERGE_* >output 2>/dev/null &&
+	test_cmp /dev/null output &&
+	# Merge commit has pre-merge y and pre-merge z as parents
+	test "$(git rev-parse refs/notes/m^1)" = "$(cat pre_merge_y)" &&
+	test "$(git rev-parse refs/notes/m^2)" = "$(cat pre_merge_z)" &&
+	# Merge commit mentions the notes refs merged
+	git log -1 --format=%B refs/notes/m > merge_commit_msg &&
+	grep -q refs/notes/m merge_commit_msg &&
+	grep -q refs/notes/z merge_commit_msg &&
+	# Verify contents of merge result
+	verify_notes m &&
+	# Verify that other notes refs has not changed (w, x, y and z)
+	verify_notes w &&
+	verify_notes x &&
+	verify_notes y &&
+	verify_notes z
+'
+
 test_done
-- 
1.7.3.98.g5ad7d9

[PATCHv5 17/23] git notes merge: List conflicting notes in notes merge commit message

[Johan Herland]

This brings notes merge in line with regular merge's behaviour.

This patch has been improved by the following contributions:
- Ævar Arnfjörð Bjarmason: Don't use C99 comments.

Thanks-to: Ævar Arnfjörð Bjarmason <avarab@gmail.com>
Signed-off-by: Johan Herland <johan@herland.net>
---
 builtin/notes.c                       |    2 +-
 notes-merge.c                         |   11 ++++++++++-
 notes-merge.h                         |    2 +-
 t/t3310-notes-merge-manual-resolve.sh |   12 ++++++++++++
 4 files changed, 24 insertions(+), 3 deletions(-)

diff --git a/builtin/notes.c b/builtin/notes.c
index db60ead..b440378 100644
--- a/builtin/notes.c
+++ b/builtin/notes.c
@@ -902,7 +902,7 @@ static int merge(int argc, const char **argv, const char *prefix)
 
 	strbuf_addf(&msg, "notes: Merged notes from %s into %s",
 		    remote_ref.buf, default_notes_ref());
-	o.commit_msg = msg.buf + 7; // skip "notes: " prefix
+	strbuf_add(&(o.commit_msg), msg.buf + 7, msg.len - 7); /* skip "notes: " */
 
 	result = notes_merge(&o, t, result_sha1);
 
diff --git a/notes-merge.c b/notes-merge.c
index b44273c..db4fe08 100644
--- a/notes-merge.c
+++ b/notes-merge.c
@@ -8,6 +8,7 @@
 #include "dir.h"
 #include "notes.h"
 #include "notes-merge.h"
+#include "strbuf.h"
 
 struct notes_merge_pair {
 	unsigned char obj[20], base[20], local[20], remote[20];
@@ -16,6 +17,7 @@ struct notes_merge_pair {
 void init_notes_merge_options(struct notes_merge_options *o)
 {
 	memset(o, 0, sizeof(struct notes_merge_options));
+	strbuf_init(&(o->commit_msg), 0);
 	o->verbosity = NOTES_MERGE_VERBOSITY_DEFAULT;
 }
 
@@ -384,6 +386,12 @@ static int merge_one_change_manual(struct notes_merge_options *o,
 	       sha1_to_hex(p->obj), sha1_to_hex(p->base),
 	       sha1_to_hex(p->local), sha1_to_hex(p->remote));
 
+	/* add "Conflicts:" section to commit message first time through */
+	if (!o->has_worktree)
+		strbuf_addstr(&(o->commit_msg), "\n\nConflicts:\n");
+
+	strbuf_addf(&(o->commit_msg), "\t%s\n", sha1_to_hex(p->obj));
+
 	OUTPUT(o, 2, "Auto-merging notes for %s", sha1_to_hex(p->obj));
 	check_notes_merge_worktree(o);
 	if (is_null_sha1(p->local)) {
@@ -639,12 +647,13 @@ int notes_merge(struct notes_merge_options *o,
 		struct commit_list *parents = NULL;
 		commit_list_insert(remote, &parents); /* LIFO order */
 		commit_list_insert(local, &parents);
-		create_notes_commit(local_tree, parents, o->commit_msg,
+		create_notes_commit(local_tree, parents, o->commit_msg.buf,
 				    result_sha1);
 	}
 
 found_result:
 	free_commit_list(bases);
+	strbuf_release(&(o->commit_msg));
 	trace_printf("notes_merge(): result = %i, result_sha1 = %.7s\n",
 	       result, sha1_to_hex(result_sha1));
 	return result;
diff --git a/notes-merge.h b/notes-merge.h
index aa75693..195222f 100644
--- a/notes-merge.h
+++ b/notes-merge.h
@@ -11,7 +11,7 @@ enum notes_merge_verbosity {
 struct notes_merge_options {
 	const char *local_ref;
 	const char *remote_ref;
-	const char *commit_msg;
+	struct strbuf commit_msg;
 	int verbosity;
 	enum {
 		NOTES_MERGE_RESOLVE_MANUAL = 0,
diff --git a/t/t3310-notes-merge-manual-resolve.sh b/t/t3310-notes-merge-manual-resolve.sh
index 0ec315a..287fab8 100755
--- a/t/t3310-notes-merge-manual-resolve.sh
+++ b/t/t3310-notes-merge-manual-resolve.sh
@@ -333,6 +333,12 @@ EOF
 	git log -1 --format=%B refs/notes/m > merge_commit_msg &&
 	grep -q refs/notes/m merge_commit_msg &&
 	grep -q refs/notes/z merge_commit_msg &&
+	# Merge commit mentions conflicting notes
+	grep -q "Conflicts" merge_commit_msg &&
+	( for sha1 in $(cat expect_conflicts); do
+		grep -q "$sha1" merge_commit_msg ||
+		exit 1
+	done ) &&
 	# Verify contents of merge result
 	verify_notes m &&
 	# Verify that other notes refs has not changed (w, x, y and z)
@@ -456,6 +462,12 @@ EOF
 	git log -1 --format=%B refs/notes/m > merge_commit_msg &&
 	grep -q refs/notes/m merge_commit_msg &&
 	grep -q refs/notes/z merge_commit_msg &&
+	# Merge commit mentions conflicting notes
+	grep -q "Conflicts" merge_commit_msg &&
+	( for sha1 in $(cat expect_conflicts); do
+		grep -q "$sha1" merge_commit_msg ||
+		exit 1
+	done ) &&
 	# Verify contents of merge result
 	verify_notes m &&
 	# Verify that other notes refs has not changed (w, x, y and z)
-- 
1.7.3.98.g5ad7d9

[PATCHv5 18/23] git notes merge: --commit should fail if underlying notes ref has moved

[Johan Herland]

When manually resolving a notes merge, if the merging ref has moved since
the merge started, we should fail to complete the merge, and alert the user
to what's going on.

This situation may arise if you start a 'git notes merge' which results in
conflicts, and you then update the current notes ref (using for example
'git notes add/copy/amend/edit/remove/prune', 'git update-ref', etc.),
before you get around to resolving the notes conflicts and calling
'git notes merge --commit'.

We detect this situation by comparing the first parent of the partial merge
commit (which was created when the merge started) to the current value of the
merging notes ref (pointed to by the .git/NOTES_MERGE_REF symref).

If we don't fail in this situation, the notes merge commit would overwrite
the updated notes ref, thus losing the changes that happened in the meantime.

The patch includes a testcase verifying that we fail correctly in this
situation.

Signed-off-by: Johan Herland <johan@herland.net>
---
 builtin/notes.c                       |   11 ++++-
 t/t3310-notes-merge-manual-resolve.sh |   76 +++++++++++++++++++++++++++++++++
 2 files changed, 85 insertions(+), 2 deletions(-)

diff --git a/builtin/notes.c b/builtin/notes.c
index b440378..ca09d45 100644
--- a/builtin/notes.c
+++ b/builtin/notes.c
@@ -786,7 +786,7 @@ static int merge_abort(struct notes_merge_options *o)
 static int merge_commit(struct notes_merge_options *o)
 {
 	struct strbuf msg = STRBUF_INIT;
-	unsigned char sha1[20];
+	unsigned char sha1[20], parent_sha1[20];
 	struct notes_tree *t;
 	struct commit *partial;
 	struct pretty_print_context pretty_ctx;
@@ -803,6 +803,11 @@ static int merge_commit(struct notes_merge_options *o)
 	else if (parse_commit(partial))
 		die("Could not parse commit from NOTES_MERGE_PARTIAL.");
 
+	if (partial->parents)
+		hashcpy(parent_sha1, partial->parents->item->object.sha1);
+	else
+		hashclr(parent_sha1);
+
 	t = xcalloc(1, sizeof(struct notes_tree));
 	init_notes(t, "NOTES_MERGE_PARTIAL", combine_notes_overwrite, 0);
 
@@ -818,7 +823,9 @@ static int merge_commit(struct notes_merge_options *o)
 	format_commit_message(partial, "%s", &msg, &pretty_ctx);
 	strbuf_trim(&msg);
 	strbuf_insert(&msg, 0, "notes: ", 7);
-	update_ref(msg.buf, o->local_ref, sha1, NULL, 0, DIE_ON_ERR);
+	update_ref(msg.buf, o->local_ref, sha1,
+		   is_null_sha1(parent_sha1) ? NULL : parent_sha1,
+		   0, DIE_ON_ERR);
 
 	free_notes(t);
 	strbuf_release(&msg);
diff --git a/t/t3310-notes-merge-manual-resolve.sh b/t/t3310-notes-merge-manual-resolve.sh
index 287fab8..4ec4d11 100755
--- a/t/t3310-notes-merge-manual-resolve.sh
+++ b/t/t3310-notes-merge-manual-resolve.sh
@@ -477,4 +477,80 @@ EOF
 	verify_notes z
 '
 
+cp expect_notes_y expect_notes_m
+cp expect_log_y expect_log_m
+
+test_expect_success 'redo merge of z into m (== y) with default ("manual") resolver => Conflicting 3-way merge' '
+	git update-ref refs/notes/m refs/notes/y &&
+	test_must_fail git notes merge z >output &&
+	# Output should point to where to resolve conflicts
+	grep -q "\\.git/NOTES_MERGE_WORKTREE" output &&
+	# Inspect merge conflicts
+	ls .git/NOTES_MERGE_WORKTREE >output_conflicts &&
+	test_cmp expect_conflicts output_conflicts &&
+	( for f in $(cat expect_conflicts); do
+		test_cmp "expect_conflict_$f" ".git/NOTES_MERGE_WORKTREE/$f" ||
+		exit 1
+	done ) &&
+	# Verify that current notes tree (pre-merge) has not changed (m == y)
+	verify_notes y &&
+	verify_notes m &&
+	test "$(git rev-parse refs/notes/m)" = "$(cat pre_merge_y)"
+'
+
+cp expect_notes_w expect_notes_m
+cp expect_log_w expect_log_m
+
+test_expect_success 'reset notes ref m to somewhere else (w)' '
+	git update-ref refs/notes/m refs/notes/w &&
+	verify_notes m &&
+	test "$(git rev-parse refs/notes/m)" = "$(git rev-parse refs/notes/w)"
+'
+
+test_expect_success 'fail to finalize conflicting merge if underlying ref has moved in the meantime (m != NOTES_MERGE_PARTIAL^1)' '
+	# Resolve conflicts
+	cat >.git/NOTES_MERGE_WORKTREE/$commit_sha1 <<EOF &&
+y and z notes on 1st commit
+EOF
+	cat >.git/NOTES_MERGE_WORKTREE/$commit_sha4 <<EOF &&
+y and z notes on 4th commit
+EOF
+	# Fail to finalize merge
+	test_must_fail git notes merge --commit >output 2>&1 &&
+	# .git/NOTES_MERGE_* must remain
+	test -f .git/NOTES_MERGE_PARTIAL &&
+	test -f .git/NOTES_MERGE_REF &&
+	test -f .git/NOTES_MERGE_WORKTREE/$commit_sha1 &&
+	test -f .git/NOTES_MERGE_WORKTREE/$commit_sha2 &&
+	test -f .git/NOTES_MERGE_WORKTREE/$commit_sha3 &&
+	test -f .git/NOTES_MERGE_WORKTREE/$commit_sha4 &&
+	# Refs are unchanged
+	test "$(git rev-parse refs/notes/m)" = "$(git rev-parse refs/notes/w)"
+	test "$(git rev-parse refs/notes/y)" = "$(git rev-parse NOTES_MERGE_PARTIAL^1)"
+	test "$(git rev-parse refs/notes/m)" != "$(git rev-parse NOTES_MERGE_PARTIAL^1)"
+	# Mention refs/notes/m, and its current and expected value in output
+	grep -q "refs/notes/m" output &&
+	grep -q "$(git rev-parse refs/notes/m)" output &&
+	grep -q "$(git rev-parse NOTES_MERGE_PARTIAL^1)" output &&
+	# Verify that other notes refs has not changed (w, x, y and z)
+	verify_notes w &&
+	verify_notes x &&
+	verify_notes y &&
+	verify_notes z
+'
+
+test_expect_success 'resolve situation by aborting the notes merge' '
+	git notes merge --abort &&
+	# No .git/NOTES_MERGE_* files left
+	test_must_fail ls .git/NOTES_MERGE_* >output 2>/dev/null &&
+	test_cmp /dev/null output &&
+	# m has not moved (still == w)
+	test "$(git rev-parse refs/notes/m)" = "$(git rev-parse refs/notes/w)"
+	# Verify that other notes refs has not changed (w, x, y and z)
+	verify_notes w &&
+	verify_notes x &&
+	verify_notes y &&
+	verify_notes z
+'
+
 test_done
-- 
1.7.3.98.g5ad7d9

[PATCHv5 19/23] git notes merge: Add another auto-resolving strategy: "cat_sort_uniq"

[Johan Herland]

This new strategy is similar to "concatenate", but in addition to
concatenating the two note candidates, this strategy sorts the resulting
lines, and removes duplicate lines from the result. This is equivalent to
applying the "cat | sort | uniq" shell pipeline to the two note candidates.

This strategy is useful if the notes follow a line-based format where one
wants to avoid duplicate lines in the merge result.

Note that if either of the note candidates contain duplicate lines _prior_
to the merge, these will also be removed by this merge strategy.

The patch also contains tests and documentation for the new strategy.

Signed-off-by: Johan Herland <johan@herland.net>
---
 Documentation/git-notes.txt         |   12 +++-
 builtin/notes.c                     |    8 ++-
 notes-merge.c                       |    6 ++
 notes-merge.h                       |    3 +-
 notes.c                             |   76 ++++++++++++++++++
 notes.h                             |    1 +
 t/t3309-notes-merge-auto-resolve.sh |  145 +++++++++++++++++++++++++++++++++++
 7 files changed, 247 insertions(+), 4 deletions(-)

diff --git a/Documentation/git-notes.txt b/Documentation/git-notes.txt
index a822551..1de1417 100644
--- a/Documentation/git-notes.txt
+++ b/Documentation/git-notes.txt
@@ -155,7 +155,7 @@ OPTIONS
 --strategy=<strategy>::
 	When merging notes, resolve notes conflicts using the given
 	strategy. The following strategies are recognized: "manual"
-	(default), "ours", "theirs" and "union".
+	(default), "ours", "theirs", "union" and "cat_sort_uniq".
 	See the "NOTES MERGE STRATEGIES" section below for more
 	information on each notes merge strategy.
 
@@ -230,6 +230,16 @@ ref).
 "union" automatically resolves notes conflicts by concatenating the
 local and remote versions.
 
+"cat_sort_uniq" is similar to "union", but in addition to concatenating
+the local and remote versions, this strategy also sorts the resulting
+lines, and removes duplicate lines from the result. This is equivalent
+to applying the "cat | sort | uniq" shell pipeline to the local and
+remote versions. This strategy is useful if the notes follow a line-based
+format where one wants to avoid duplicated lines in the merge result.
+Note that if either the local or remote version contain duplicate lines
+prior to the merge, these will also be removed by this notes merge
+strategy.
+
 
 EXAMPLES
 --------
diff --git a/builtin/notes.c b/builtin/notes.c
index ca09d45..79783a5 100644
--- a/builtin/notes.c
+++ b/builtin/notes.c
@@ -324,6 +324,8 @@ combine_notes_fn parse_combine_notes_fn(const char *v)
 		return combine_notes_ignore;
 	else if (!strcasecmp(v, "concatenate"))
 		return combine_notes_concatenate;
+	else if (!strcasecmp(v, "cat_sort_uniq"))
+		return combine_notes_cat_sort_uniq;
 	else
 		return NULL;
 }
@@ -846,8 +848,8 @@ static int merge(int argc, const char **argv, const char *prefix)
 		OPT__VERBOSITY(&verbosity),
 		OPT_GROUP("Merge options"),
 		OPT_STRING('s', "strategy", &strategy, "strategy",
-			   "resolve notes conflicts using the given "
-			   "strategy (manual/ours/theirs/union)"),
+			   "resolve notes conflicts using the given strategy "
+			   "(manual/ours/theirs/union/cat_sort_uniq)"),
 		OPT_GROUP("Committing unmerged notes"),
 		{ OPTION_BOOLEAN, 0, "commit", &do_commit, NULL,
 			"finalize notes merge by committing unmerged notes",
@@ -899,6 +901,8 @@ static int merge(int argc, const char **argv, const char *prefix)
 			o.strategy = NOTES_MERGE_RESOLVE_THEIRS;
 		else if (!strcmp(strategy, "union"))
 			o.strategy = NOTES_MERGE_RESOLVE_UNION;
+		else if (!strcmp(strategy, "cat_sort_uniq"))
+			o.strategy = NOTES_MERGE_RESOLVE_CAT_SORT_UNIQ;
 		else {
 			error("Unknown -s/--strategy: %s", strategy);
 			usage_with_options(git_notes_merge_usage, options);
diff --git a/notes-merge.c b/notes-merge.c
index db4fe08..d112a91 100644
--- a/notes-merge.c
+++ b/notes-merge.c
@@ -452,6 +452,12 @@ static int merge_one_change(struct notes_merge_options *o,
 		if (add_note(t, p->obj, p->remote, combine_notes_concatenate))
 			die("confused: combine_notes_concatenate failed");
 		return 0;
+	case NOTES_MERGE_RESOLVE_CAT_SORT_UNIQ:
+		OUTPUT(o, 2, "Concatenating unique lines in local and remote "
+		       "notes for %s", sha1_to_hex(p->obj));
+		if (add_note(t, p->obj, p->remote, combine_notes_cat_sort_uniq))
+			die("confused: combine_notes_cat_sort_uniq failed");
+		return 0;
 	}
 	die("Unknown strategy (%i).", o->strategy);
 }
diff --git a/notes-merge.h b/notes-merge.h
index 195222f..168a672 100644
--- a/notes-merge.h
+++ b/notes-merge.h
@@ -17,7 +17,8 @@ struct notes_merge_options {
 		NOTES_MERGE_RESOLVE_MANUAL = 0,
 		NOTES_MERGE_RESOLVE_OURS,
 		NOTES_MERGE_RESOLVE_THEIRS,
-		NOTES_MERGE_RESOLVE_UNION
+		NOTES_MERGE_RESOLVE_UNION,
+		NOTES_MERGE_RESOLVE_CAT_SORT_UNIQ
 	} strategy;
 	unsigned has_worktree:1;
 };
diff --git a/notes.c b/notes.c
index 09a93ab..96cde42 100644
--- a/notes.c
+++ b/notes.c
@@ -845,6 +845,82 @@ int combine_notes_ignore(unsigned char *cur_sha1,
 	return 0;
 }
 
+static int string_list_add_note_lines(struct string_list *sort_uniq_list,
+				      const unsigned char *sha1)
+{
+	char *data;
+	unsigned long len;
+	enum object_type t;
+	struct strbuf buf = STRBUF_INIT;
+	struct strbuf **lines = NULL;
+	int i, list_index;
+
+	if (is_null_sha1(sha1))
+		return 0;
+
+	/* read_sha1_file NUL-terminates */
+	data = read_sha1_file(sha1, &t, &len);
+	if (t != OBJ_BLOB || !data || !len) {
+		free(data);
+		return t != OBJ_BLOB || !data;
+	}
+
+	strbuf_attach(&buf, data, len, len + 1);
+	lines = strbuf_split(&buf, '\n');
+
+	for (i = 0; lines[i]; i++) {
+		if (lines[i]->buf[lines[i]->len - 1] == '\n')
+			strbuf_setlen(lines[i], lines[i]->len - 1);
+		if (!lines[i]->len)
+			continue; /* skip empty lines */
+		list_index = string_list_find_insert_index(sort_uniq_list,
+							   lines[i]->buf, 0);
+		if (list_index < 0)
+			continue; /* skip duplicate lines */
+		string_list_insert_at_index(sort_uniq_list, list_index,
+					    lines[i]->buf);
+	}
+
+	strbuf_list_free(lines);
+	strbuf_release(&buf);
+	return 0;
+}
+
+static int string_list_join_lines_helper(struct string_list_item *item,
+					 void *cb_data)
+{
+	struct strbuf *buf = cb_data;
+	strbuf_addstr(buf, item->string);
+	strbuf_addch(buf, '\n');
+	return 0;
+}
+
+int combine_notes_cat_sort_uniq(unsigned char *cur_sha1,
+		const unsigned char *new_sha1)
+{
+	struct string_list sort_uniq_list = { NULL, 0, 0, 1 };
+	struct strbuf buf = STRBUF_INIT;
+	int ret = 1;
+
+	/* read both note blob objects into unique_lines */
+	if (string_list_add_note_lines(&sort_uniq_list, cur_sha1))
+		goto out;
+	if (string_list_add_note_lines(&sort_uniq_list, new_sha1))
+		goto out;
+
+	/* create a new blob object from sort_uniq_list */
+	if (for_each_string_list(&sort_uniq_list,
+				 string_list_join_lines_helper, &buf))
+		goto out;
+
+	ret = write_sha1_file(buf.buf, buf.len, blob_type, cur_sha1);
+
+out:
+	strbuf_release(&buf);
+	string_list_clear(&sort_uniq_list, 0);
+	return ret;
+}
+
 static int string_list_add_one_ref(const char *path, const unsigned char *sha1,
 				   int flag, void *cb)
 {
diff --git a/notes.h b/notes.h
index b372575..93a7365 100644
--- a/notes.h
+++ b/notes.h
@@ -27,6 +27,7 @@ typedef int (*combine_notes_fn)(unsigned char *cur_sha1, const unsigned char *ne
 int combine_notes_concatenate(unsigned char *cur_sha1, const unsigned char *new_sha1);
 int combine_notes_overwrite(unsigned char *cur_sha1, const unsigned char *new_sha1);
 int combine_notes_ignore(unsigned char *cur_sha1, const unsigned char *new_sha1);
+int combine_notes_cat_sort_uniq(unsigned char *cur_sha1, const unsigned char *new_sha1);
 
 /*
  * Notes tree object
diff --git a/t/t3309-notes-merge-auto-resolve.sh b/t/t3309-notes-merge-auto-resolve.sh
index 1a1fc7e..461fd84 100755
--- a/t/t3309-notes-merge-auto-resolve.sh
+++ b/t/t3309-notes-merge-auto-resolve.sh
@@ -499,4 +499,149 @@ test_expect_success 'merge z into y with "union" strategy => Non-conflicting 3-w
 	verify_notes y union
 '
 
+test_expect_success 'reset to pre-merge state (y)' '
+	git update-ref refs/notes/y refs/notes/y^1 &&
+	# Verify pre-merge state
+	verify_notes y y
+'
+
+cat <<EOF | sort >expect_notes_union2
+d682107b8bf7a7aea1e537a8d5cb6a12b60135f1 $commit_sha15
+5de7ea7ad4f47e7ff91989fb82234634730f75df $commit_sha14
+3a631fdb6f41b05b55d8f4baf20728ba8f6fccbc $commit_sha13
+a66055fa82f7a03fe0c02a6aba3287a85abf7c62 $commit_sha12
+7e3c53503a3db8dd996cb62e37c66e070b44b54d $commit_sha11
+b8d03e173f67f6505a76f6e00cf93440200dd9be $commit_sha10
+851e1638784a884c7dd26c5d41f3340f6387413a $commit_sha8
+357b6ca14c7afd59b7f8b8aaaa6b8b723771135b $commit_sha5
+e2bfd06a37dd2031684a59a6e2b033e212239c78 $commit_sha4
+5772f42408c0dd6f097a7ca2d24de0e78d1c46b1 $commit_sha3
+283b48219aee9a4105f6cab337e789065c82c2b9 $commit_sha2
+EOF
+
+cat >expect_log_union2 <<EOF
+$commit_sha15 15th
+z notes on 15th commit
+
+y notes on 15th commit
+
+$commit_sha14 14th
+y notes on 14th commit
+
+$commit_sha13 13th
+y notes on 13th commit
+
+$commit_sha12 12th
+y notes on 12th commit
+
+$commit_sha11 11th
+z notes on 11th commit
+
+$commit_sha10 10th
+x notes on 10th commit
+
+$commit_sha9 9th
+
+$commit_sha8 8th
+z notes on 8th commit
+
+$commit_sha7 7th
+
+$commit_sha6 6th
+
+$commit_sha5 5th
+z notes on 5th commit
+
+y notes on 5th commit
+
+$commit_sha4 4th
+y notes on 4th commit
+
+$commit_sha3 3rd
+y notes on 3rd commit
+
+$commit_sha2 2nd
+z notes on 2nd commit
+
+$commit_sha1 1st
+
+EOF
+
+test_expect_success 'merge y into z with "union" strategy => Non-conflicting 3-way merge' '
+	git config core.notesRef refs/notes/z &&
+	git notes merge --strategy=union y &&
+	verify_notes z union2
+'
+
+test_expect_success 'reset to pre-merge state (z)' '
+	git update-ref refs/notes/z refs/notes/z^1 &&
+	# Verify pre-merge state
+	verify_notes z z
+'
+
+cat <<EOF | sort >expect_notes_cat_sort_uniq
+6be90240b5f54594203e25d9f2f64b7567175aee $commit_sha15
+5de7ea7ad4f47e7ff91989fb82234634730f75df $commit_sha14
+3a631fdb6f41b05b55d8f4baf20728ba8f6fccbc $commit_sha13
+a66055fa82f7a03fe0c02a6aba3287a85abf7c62 $commit_sha12
+7e3c53503a3db8dd996cb62e37c66e070b44b54d $commit_sha11
+b8d03e173f67f6505a76f6e00cf93440200dd9be $commit_sha10
+851e1638784a884c7dd26c5d41f3340f6387413a $commit_sha8
+660311d7f78dc53db12ac373a43fca7465381a7e $commit_sha5
+e2bfd06a37dd2031684a59a6e2b033e212239c78 $commit_sha4
+5772f42408c0dd6f097a7ca2d24de0e78d1c46b1 $commit_sha3
+283b48219aee9a4105f6cab337e789065c82c2b9 $commit_sha2
+EOF
+
+cat >expect_log_cat_sort_uniq <<EOF
+$commit_sha15 15th
+y notes on 15th commit
+z notes on 15th commit
+
+$commit_sha14 14th
+y notes on 14th commit
+
+$commit_sha13 13th
+y notes on 13th commit
+
+$commit_sha12 12th
+y notes on 12th commit
+
+$commit_sha11 11th
+z notes on 11th commit
+
+$commit_sha10 10th
+x notes on 10th commit
+
+$commit_sha9 9th
+
+$commit_sha8 8th
+z notes on 8th commit
+
+$commit_sha7 7th
+
+$commit_sha6 6th
+
+$commit_sha5 5th
+y notes on 5th commit
+z notes on 5th commit
+
+$commit_sha4 4th
+y notes on 4th commit
+
+$commit_sha3 3rd
+y notes on 3rd commit
+
+$commit_sha2 2nd
+z notes on 2nd commit
+
+$commit_sha1 1st
+
+EOF
+
+test_expect_success 'merge y into z with "cat_sort_uniq" strategy => Non-conflicting 3-way merge' '
+	git notes merge --strategy=cat_sort_uniq y &&
+	verify_notes z cat_sort_uniq
+'
+
 test_done
-- 
1.7.3.98.g5ad7d9

[PATCHv5 20/23] git notes merge: Add testcases for merging notes trees at different fanouts

[Johan Herland]

Notes trees may exist at different fanout levels internally. This
implementation detail should not be visible to the user, and it should
certainly not affect the merging of notes tree.

This patch adds testcases verifying the correctness of 'git notes merge'
when merging notes trees at different fanout levels.

Signed-off-by: Johan Herland <johan@herland.net>
---
 t/t3311-notes-merge-fanout.sh |  436 +++++++++++++++++++++++++++++++++++++++++
 1 files changed, 436 insertions(+), 0 deletions(-)
 create mode 100755 t/t3311-notes-merge-fanout.sh

diff --git a/t/t3311-notes-merge-fanout.sh b/t/t3311-notes-merge-fanout.sh
new file mode 100755
index 0000000..d1c7b69
--- /dev/null
+++ b/t/t3311-notes-merge-fanout.sh
@@ -0,0 +1,436 @@
+#!/bin/sh
+#
+# Copyright (c) 2010 Johan Herland
+#
+
+test_description='Test notes merging at various fanout levels'
+
+. ./test-lib.sh
+
+verify_notes () {
+	notes_ref="$1"
+	commit="$2"
+	if test -f "expect_notes_$notes_ref"
+	then
+		git -c core.notesRef="refs/notes/$notes_ref" notes |
+			sort >"output_notes_$notes_ref" &&
+		test_cmp "expect_notes_$notes_ref" "output_notes_$notes_ref" ||
+			return 1
+	fi &&
+	git -c core.notesRef="refs/notes/$notes_ref" log --format="%H %s%n%N" \
+		"$commit" >"output_log_$notes_ref" &&
+	test_cmp "expect_log_$notes_ref" "output_log_$notes_ref"
+}
+
+verify_fanout () {
+	notes_ref="$1"
+	# Expect entire notes tree to have a fanout == 1
+	git rev-parse --quiet --verify "refs/notes/$notes_ref" >/dev/null &&
+	git ls-tree -r --name-only "refs/notes/$notes_ref" |
+	while read path
+	do
+		case "$path" in
+		??/??????????????????????????????????????)
+			: true
+			;;
+		*)
+			echo "Invalid path \"$path\"" &&
+			return 1
+			;;
+		esac
+	done
+}
+
+verify_no_fanout () {
+	notes_ref="$1"
+	# Expect entire notes tree to have a fanout == 0
+	git rev-parse --quiet --verify "refs/notes/$notes_ref" >/dev/null &&
+	git ls-tree -r --name-only "refs/notes/$notes_ref" |
+	while read path
+	do
+		case "$path" in
+		????????????????????????????????????????)
+			: true
+			;;
+		*)
+			echo "Invalid path \"$path\"" &&
+			return 1
+			;;
+		esac
+	done
+}
+
+# Set up a notes merge scenario with different kinds of conflicts
+test_expect_success 'setup a few initial commits with notes (notes ref: x)' '
+	git config core.notesRef refs/notes/x &&
+	for i in 1 2 3 4 5
+	do
+		test_commit "commit$i" >/dev/null &&
+		git notes add -m "notes for commit$i" || return 1
+	done
+'
+
+commit_sha1=$(git rev-parse commit1^{commit})
+commit_sha2=$(git rev-parse commit2^{commit})
+commit_sha3=$(git rev-parse commit3^{commit})
+commit_sha4=$(git rev-parse commit4^{commit})
+commit_sha5=$(git rev-parse commit5^{commit})
+
+cat <<EOF | sort >expect_notes_x
+aed91155c7a72c2188e781fdf40e0f3761b299db $commit_sha5
+99fab268f9d7ee7b011e091a436c78def8eeee69 $commit_sha4
+953c20ae26c7aa0b428c20693fe38bc687f9d1a9 $commit_sha3
+6358796131b8916eaa2dde6902642942a1cb37e1 $commit_sha2
+b02d459c32f0e68f2fe0981033bb34f38776ba47 $commit_sha1
+EOF
+
+cat >expect_log_x <<EOF
+$commit_sha5 commit5
+notes for commit5
+
+$commit_sha4 commit4
+notes for commit4
+
+$commit_sha3 commit3
+notes for commit3
+
+$commit_sha2 commit2
+notes for commit2
+
+$commit_sha1 commit1
+notes for commit1
+
+EOF
+
+test_expect_success 'sanity check (x)' '
+	verify_notes x commit5 &&
+	verify_no_fanout x
+'
+
+num=300
+
+cp expect_log_x expect_log_y
+
+test_expect_success 'Add a few hundred commits w/notes to trigger fanout (x -> y)' '
+	git update-ref refs/notes/y refs/notes/x &&
+	git config core.notesRef refs/notes/y &&
+	i=5 &&
+	while test $i -lt $num
+	do
+		i=$(($i + 1)) &&
+		test_commit "commit$i" >/dev/null &&
+		git notes add -m "notes for commit$i" || return 1
+	done &&
+	test "$(git rev-parse refs/notes/y)" != "$(git rev-parse refs/notes/x)" &&
+	# Expected number of commits and notes
+	test "$(git rev-list HEAD | wc -l)" = "$num" &&
+	test "$(git notes list | wc -l)" = "$num" &&
+	# 5 first notes unchanged
+	verify_notes y commit5
+'
+
+test_expect_success 'notes tree has fanout (y)' 'verify_fanout y'
+
+test_expect_success 'No-op merge (already included) (x => y)' '
+	git update-ref refs/notes/m refs/notes/y &&
+	git config core.notesRef refs/notes/m &&
+	git notes merge x &&
+	test "$(git rev-parse refs/notes/m)" = "$(git rev-parse refs/notes/y)"
+'
+
+test_expect_success 'Fast-forward merge (y => x)' '
+	git update-ref refs/notes/m refs/notes/x &&
+	git notes merge y &&
+	test "$(git rev-parse refs/notes/m)" = "$(git rev-parse refs/notes/y)"
+'
+
+cat <<EOF | sort >expect_notes_z
+9f506ee70e20379d7f78204c77b334f43d77410d $commit_sha3
+23a47d6ea7d589895faf800752054818e1e7627b $commit_sha2
+b02d459c32f0e68f2fe0981033bb34f38776ba47 $commit_sha1
+EOF
+
+cat >expect_log_z <<EOF
+$commit_sha5 commit5
+
+$commit_sha4 commit4
+
+$commit_sha3 commit3
+notes for commit3
+
+appended notes for commit3
+
+$commit_sha2 commit2
+new notes for commit2
+
+$commit_sha1 commit1
+notes for commit1
+
+EOF
+
+test_expect_success 'change some of the initial 5 notes (x -> z)' '
+	git update-ref refs/notes/z refs/notes/x &&
+	git config core.notesRef refs/notes/z &&
+	git notes add -f -m "new notes for commit2" commit2 &&
+	git notes append -m "appended notes for commit3" commit3 &&
+	git notes remove commit4 &&
+	git notes remove commit5 &&
+	verify_notes z commit5
+'
+
+test_expect_success 'notes tree has no fanout (z)' 'verify_no_fanout z'
+
+cp expect_log_z expect_log_m
+
+test_expect_success 'successful merge without conflicts (y => z)' '
+	git update-ref refs/notes/m refs/notes/z &&
+	git config core.notesRef refs/notes/m &&
+	git notes merge y &&
+	verify_notes m commit5 &&
+	# x/y/z unchanged
+	verify_notes x commit5 &&
+	verify_notes y commit5 &&
+	verify_notes z commit5
+'
+
+test_expect_success 'notes tree still has fanout after merge (m)' 'verify_fanout m'
+
+cat >expect_log_w <<EOF
+$commit_sha5 commit5
+
+$commit_sha4 commit4
+other notes for commit4
+
+$commit_sha3 commit3
+other notes for commit3
+
+$commit_sha2 commit2
+notes for commit2
+
+$commit_sha1 commit1
+other notes for commit1
+
+EOF
+
+test_expect_success 'introduce conflicting changes (y -> w)' '
+	git update-ref refs/notes/w refs/notes/y &&
+	git config core.notesRef refs/notes/w &&
+	git notes add -f -m "other notes for commit1" commit1 &&
+	git notes add -f -m "other notes for commit3" commit3 &&
+	git notes add -f -m "other notes for commit4" commit4 &&
+	git notes remove commit5 &&
+	verify_notes w commit5
+'
+
+cat >expect_log_m <<EOF
+$commit_sha5 commit5
+
+$commit_sha4 commit4
+other notes for commit4
+
+$commit_sha3 commit3
+other notes for commit3
+
+$commit_sha2 commit2
+new notes for commit2
+
+$commit_sha1 commit1
+other notes for commit1
+
+EOF
+
+test_expect_success 'successful merge using "ours" strategy (z => w)' '
+	git update-ref refs/notes/m refs/notes/w &&
+	git config core.notesRef refs/notes/m &&
+	git notes merge -s ours z &&
+	verify_notes m commit5 &&
+	# w/x/y/z unchanged
+	verify_notes w commit5 &&
+	verify_notes x commit5 &&
+	verify_notes y commit5 &&
+	verify_notes z commit5
+'
+
+test_expect_success 'notes tree still has fanout after merge (m)' 'verify_fanout m'
+
+cat >expect_log_m <<EOF
+$commit_sha5 commit5
+
+$commit_sha4 commit4
+
+$commit_sha3 commit3
+notes for commit3
+
+appended notes for commit3
+
+$commit_sha2 commit2
+new notes for commit2
+
+$commit_sha1 commit1
+other notes for commit1
+
+EOF
+
+test_expect_success 'successful merge using "theirs" strategy (z => w)' '
+	git update-ref refs/notes/m refs/notes/w &&
+	git notes merge -s theirs z &&
+	verify_notes m commit5 &&
+	# w/x/y/z unchanged
+	verify_notes w commit5 &&
+	verify_notes x commit5 &&
+	verify_notes y commit5 &&
+	verify_notes z commit5
+'
+
+test_expect_success 'notes tree still has fanout after merge (m)' 'verify_fanout m'
+
+cat >expect_log_m <<EOF
+$commit_sha5 commit5
+
+$commit_sha4 commit4
+other notes for commit4
+
+$commit_sha3 commit3
+other notes for commit3
+
+notes for commit3
+
+appended notes for commit3
+
+$commit_sha2 commit2
+new notes for commit2
+
+$commit_sha1 commit1
+other notes for commit1
+
+EOF
+
+test_expect_success 'successful merge using "union" strategy (z => w)' '
+	git update-ref refs/notes/m refs/notes/w &&
+	git notes merge -s union z &&
+	verify_notes m commit5 &&
+	# w/x/y/z unchanged
+	verify_notes w commit5 &&
+	verify_notes x commit5 &&
+	verify_notes y commit5 &&
+	verify_notes z commit5
+'
+
+test_expect_success 'notes tree still has fanout after merge (m)' 'verify_fanout m'
+
+cat >expect_log_m <<EOF
+$commit_sha5 commit5
+
+$commit_sha4 commit4
+other notes for commit4
+
+$commit_sha3 commit3
+appended notes for commit3
+notes for commit3
+other notes for commit3
+
+$commit_sha2 commit2
+new notes for commit2
+
+$commit_sha1 commit1
+other notes for commit1
+
+EOF
+
+test_expect_success 'successful merge using "cat_sort_uniq" strategy (z => w)' '
+	git update-ref refs/notes/m refs/notes/w &&
+	git notes merge -s cat_sort_uniq z &&
+	verify_notes m commit5 &&
+	# w/x/y/z unchanged
+	verify_notes w commit5 &&
+	verify_notes x commit5 &&
+	verify_notes y commit5 &&
+	verify_notes z commit5
+'
+
+test_expect_success 'notes tree still has fanout after merge (m)' 'verify_fanout m'
+
+# We're merging z into w. Here are the conflicts we expect:
+#
+# commit | x -> w    | x -> z    | conflict?
+# -------|-----------|-----------|----------
+# 1      | changed   | unchanged | no, use w
+# 2      | unchanged | changed   | no, use z
+# 3      | changed   | changed   | yes (w, then z in conflict markers)
+# 4      | changed   | deleted   | yes (w)
+# 5      | deleted   | deleted   | no, deleted
+
+test_expect_success 'fails to merge using "manual" strategy (z => w)' '
+	git update-ref refs/notes/m refs/notes/w &&
+	test_must_fail git notes merge z
+'
+
+test_expect_success 'notes tree still has fanout after merge (m)' 'verify_fanout m'
+
+cat <<EOF | sort >expect_conflicts
+$commit_sha3
+$commit_sha4
+EOF
+
+cat >expect_conflict_$commit_sha3 <<EOF
+<<<<<<< refs/notes/m
+other notes for commit3
+=======
+notes for commit3
+
+appended notes for commit3
+>>>>>>> refs/notes/z
+EOF
+
+cat >expect_conflict_$commit_sha4 <<EOF
+other notes for commit4
+EOF
+
+test_expect_success 'verify conflict entries (with no fanout)' '
+	ls .git/NOTES_MERGE_WORKTREE >output_conflicts &&
+	test_cmp expect_conflicts output_conflicts &&
+	( for f in $(cat expect_conflicts); do
+		test_cmp "expect_conflict_$f" ".git/NOTES_MERGE_WORKTREE/$f" ||
+		exit 1
+	done ) &&
+	# Verify that current notes tree (pre-merge) has not changed (m == w)
+	test "$(git rev-parse refs/notes/m)" = "$(git rev-parse refs/notes/w)"
+'
+
+cat >expect_log_m <<EOF
+$commit_sha5 commit5
+
+$commit_sha4 commit4
+other notes for commit4
+
+$commit_sha3 commit3
+other notes for commit3
+
+appended notes for commit3
+
+$commit_sha2 commit2
+new notes for commit2
+
+$commit_sha1 commit1
+other notes for commit1
+
+EOF
+
+test_expect_success 'resolve and finalize merge (z => w)' '
+	cat >.git/NOTES_MERGE_WORKTREE/$commit_sha3 <<EOF &&
+other notes for commit3
+
+appended notes for commit3
+EOF
+	git notes merge --commit &&
+	verify_notes m commit5 &&
+	# w/x/y/z unchanged
+	verify_notes w commit5 &&
+	verify_notes x commit5 &&
+	verify_notes y commit5 &&
+	verify_notes z commit5
+'
+
+test_expect_success 'notes tree still has fanout after merge (m)' 'verify_fanout m'
+
+test_done
-- 
1.7.3.98.g5ad7d9

Re: [PATCHv5 20/23] git notes merge: Add testcases for merging notes trees at different fanouts

[Junio C Hamano]

Subject: [PATCH] portability fix for [20/23]

    test "$(line generator | wc -l)" = $expected_number_of_lines (bad)

is not portable, as "wc -l" can prefix the number with whitespaces.

Either write the $(... | wc -l) without enclosing in a dq pair, i.e.

    test $(line generator | wc -l) = $expected_number_of_lines (good)

or compare them numerically with 

    test "$(... | wc -l)" -eq $num (ok)

The former is preferred for readability.

---
 t/t3311-notes-merge-fanout.sh |    4 ++--
 1 files changed, 2 insertions(+), 2 deletions(-)

diff --git a/t/t3311-notes-merge-fanout.sh b/t/t3311-notes-merge-fanout.sh
index d1c7b69..93516ef 100755
--- a/t/t3311-notes-merge-fanout.sh
+++ b/t/t3311-notes-merge-fanout.sh
@@ -123,8 +123,8 @@ test_expect_success 'Add a few hundred commits w/notes to trigger fanout (x -> y
 	done &&
 	test "$(git rev-parse refs/notes/y)" != "$(git rev-parse refs/notes/x)" &&
 	# Expected number of commits and notes
-	test "$(git rev-list HEAD | wc -l)" = "$num" &&
-	test "$(git notes list | wc -l)" = "$num" &&
+	test $(git rev-list HEAD | wc -l) = $num &&
+	test $(git notes list | wc -l) = $num &&
 	# 5 first notes unchanged
 	verify_notes y commit5
 '
-- 
1.7.3.2.193.g78bbb

Re: [PATCHv5 20/23] git notes merge: Add testcases for merging notes trees at different fanouts

[Johan Herland]

On Friday 29 October 2010, Junio C Hamano wrote:
> Subject: [PATCH] portability fix for [20/23]
> 
>     test "$(line generator | wc -l)" = $expected_number_of_lines (bad)
> 
> is not portable, as "wc -l" can prefix the number with whitespaces.
> 
> Either write the $(... | wc -l) without enclosing in a dq pair, i.e.
> 
>     test $(line generator | wc -l) = $expected_number_of_lines (good)
> 
> or compare them numerically with
> 
>     test "$(... | wc -l)" -eq $num (ok)
> 
> The former is preferred for readability.

Ack. I'll fold this fix into the next iteration.

Thanks!

...Johan

-- 
Johan Herland, <johan@herland.net>
www.herland.net

[PATCHv5 21/23] Provide 'git notes get-ref' to easily retrieve current notes ref

[Johan Herland]

Script may use 'git notes get-ref' to easily retrieve the current notes ref.

Suggested-by: Jonathan Nieder <jrnieder@gmail.com>
Signed-off-by: Johan Herland <johan@herland.net>
---
 Documentation/git-notes.txt |    5 +++++
 builtin/notes.c             |   23 +++++++++++++++++++++++
 t/t3301-notes.sh            |   19 +++++++++++++++++++
 3 files changed, 47 insertions(+), 0 deletions(-)

diff --git a/Documentation/git-notes.txt b/Documentation/git-notes.txt
index 1de1417..296f314 100644
--- a/Documentation/git-notes.txt
+++ b/Documentation/git-notes.txt
@@ -19,6 +19,7 @@ SYNOPSIS
 'git notes' merge --abort [-v | -q]
 'git notes' remove [<object>]
 'git notes' prune [-n | -v]
+'git notes' get-ref
 
 
 DESCRIPTION
@@ -109,6 +110,10 @@ remove::
 prune::
 	Remove all notes for non-existing/unreachable objects.
 
+get-ref::
+	Print the current notes ref. This provides an easy way to
+	retrieve the current notes ref (e.g. from scripts).
+
 OPTIONS
 -------
 -f::
diff --git a/builtin/notes.c b/builtin/notes.c
index 79783a5..ef52ffd 100644
--- a/builtin/notes.c
+++ b/builtin/notes.c
@@ -31,6 +31,7 @@ static const char * const git_notes_usage[] = {
 	"git notes merge --abort [-v | -q]",
 	"git notes [--ref <notes_ref>] remove [<object>]",
 	"git notes [--ref <notes_ref>] prune [-n | -v]",
+	"git notes [--ref <notes_ref>] get-ref",
 	NULL
 };
 
@@ -82,6 +83,11 @@ static const char * const git_notes_prune_usage[] = {
 	NULL
 };
 
+static const char * const git_notes_get_ref_usage[] = {
+	"git notes get-ref",
+	NULL
+};
+
 static const char note_template[] =
 	"\n"
 	"#\n"
@@ -1002,6 +1008,21 @@ static int prune(int argc, const char **argv, const char *prefix)
 	return 0;
 }
 
+static int get_ref(int argc, const char **argv, const char *prefix)
+{
+	struct option options[] = { OPT_END() };
+	argc = parse_options(argc, argv, prefix, options,
+			     git_notes_get_ref_usage, 0);
+
+	if (argc) {
+		error("too many parameters");
+		usage_with_options(git_notes_get_ref_usage, options);
+	}
+
+	puts(default_notes_ref());
+	return 0;
+}
+
 int cmd_notes(int argc, const char **argv, const char *prefix)
 {
 	int result;
@@ -1040,6 +1061,8 @@ int cmd_notes(int argc, const char **argv, const char *prefix)
 		result = remove_cmd(argc, argv, prefix);
 	else if (!strcmp(argv[0], "prune"))
 		result = prune(argc, argv, prefix);
+	else if (!strcmp(argv[0], "get-ref"))
+		result = get_ref(argc, argv, prefix);
 	else {
 		result = error("Unknown subcommand: %s", argv[0]);
 		usage_with_options(git_notes_usage, options);
diff --git a/t/t3301-notes.sh b/t/t3301-notes.sh
index 4bf4e52..f5b72c7 100755
--- a/t/t3301-notes.sh
+++ b/t/t3301-notes.sh
@@ -1058,4 +1058,23 @@ test_expect_success 'git notes copy diagnoses too many or too few parameters' '
 	test_must_fail git notes copy one two three
 '
 
+test_expect_success 'git notes get-ref (no overrides)' '
+	git config --unset core.notesRef &&
+	unset GIT_NOTES_REF &&
+	test "$(git notes get-ref)" = "refs/notes/commits"
+'
+
+test_expect_success 'git notes get-ref (core.notesRef)' '
+	git config core.notesRef refs/notes/foo &&
+	test "$(git notes get-ref)" = "refs/notes/foo"
+'
+
+test_expect_success 'git notes get-ref (GIT_NOTES_REF)' '
+	test "$(GIT_NOTES_REF=refs/notes/bar git notes get-ref)" = "refs/notes/bar"
+'
+
+test_expect_success 'git notes get-ref (--ref)' '
+	test "$(GIT_NOTES_REF=refs/notes/bar git notes --ref=baz get-ref)" = "refs/notes/baz"
+'
+
 test_done
-- 
1.7.3.98.g5ad7d9

[PATCHv5 22/23] cmd_merge(): Parse options before checking MERGE_HEAD

[Johan Herland]

Reorder the initial part of builtin/merge.c:cmd_merge() so that command-line
options are parsed _before_ we load the index and check for MERGE_HEAD
(and exits if it exists). This does not change the behaviour of 'git merge',
but is needed in preparation for the implementation of 'git merge --abort'
(which requires MERGE_HEAD to be present).

Signed-off-by: Johan Herland <johan@herland.net>
---
 builtin/merge.c        |   33 ++++++++--------
 t/t7609-merge-abort.sh |   97 ++++++++++++++++++++++++++++++++++++++++++++++++
 2 files changed, 114 insertions(+), 16 deletions(-)
 create mode 100755 t/t7609-merge-abort.sh

diff --git a/builtin/merge.c b/builtin/merge.c
index 37ce4f5..702f399 100644
--- a/builtin/merge.c
+++ b/builtin/merge.c
@@ -895,22 +895,6 @@ int cmd_merge(int argc, const char **argv, const char *prefix)
 	const char *best_strategy = NULL, *wt_strategy = NULL;
 	struct commit_list **remotes = &remoteheads;
 
-	if (read_cache_unmerged()) {
-		die_resolve_conflict("merge");
-	}
-	if (file_exists(git_path("MERGE_HEAD"))) {
-		/*
-		 * There is no unmerged entry, don't advise 'git
-		 * add/rm <file>', just 'git commit'.
-		 */
-		if (advice_resolve_conflict)
-			die("You have not concluded your merge (MERGE_HEAD exists).\n"
-			    "Please, commit your changes before you can merge.");
-		else
-			die("You have not concluded your merge (MERGE_HEAD exists).");
-	}
-
-	resolve_undo_clear();
 	/*
 	 * Check if we are _not_ on a detached HEAD, i.e. if there is a
 	 * current branch.
@@ -929,6 +913,23 @@ int cmd_merge(int argc, const char **argv, const char *prefix)
 
 	argc = parse_options(argc, argv, prefix, builtin_merge_options,
 			builtin_merge_usage, 0);
+
+	if (read_cache_unmerged()) {
+		die_resolve_conflict("merge");
+	}
+	if (file_exists(git_path("MERGE_HEAD"))) {
+		/*
+		 * There is no unmerged entry, don't advise 'git
+		 * add/rm <file>', just 'git commit'.
+		 */
+		if (advice_resolve_conflict)
+			die("You have not concluded your merge (MERGE_HEAD exists).\n"
+			    "Please, commit your changes before you can merge.");
+		else
+			die("You have not concluded your merge (MERGE_HEAD exists).");
+	}
+	resolve_undo_clear();
+
 	if (verbosity < 0)
 		show_diffstat = 0;
 
diff --git a/t/t7609-merge-abort.sh b/t/t7609-merge-abort.sh
new file mode 100755
index 0000000..88d76e1
--- /dev/null
+++ b/t/t7609-merge-abort.sh
@@ -0,0 +1,97 @@
+#!/bin/sh
+
+test_description='test aborting in-progress merges'
+. ./test-lib.sh
+
+# Test git merge --abort with the following variables:
+# - before/after successful merge (i.e. should fail if not in merge context)
+# - with/without conflicts
+# - clean/dirty worktree before merge (may fail to reconstruct dirty worktree)
+# - clean/dirty index before merge (merge should fail on dirty index)
+# - changed/unchanged worktree after merge
+# - changed/unchanged index after merge
+
+test_done
+
+test_expect_success 'fails without MERGE_HEAD (unstarted merge)' '
+	test_must_fail git merge --abort 2>output &&
+	grep -q MERGE_HEAD output
+'
+
+test_expect_success 'fails without MERGE_HEAD (completed merge)' '
+	test_commit master-1 &&
+	test_commit master-2 &&
+	git checkout -b side HEAD^ &&
+	test_commit side-1 &&
+	git checkout master &&
+	git merge side &&
+	# Merge successfully completed
+	test_must_fail git merge --abort 2>output &&
+	grep -q MERGE_HEAD output
+'
+
+test_expect_success 'Abort successfully after --no-commit' '
+	# Forget previous merge
+	git reset --hard master^ &&
+	head=$(git rev-parse HEAD) &&
+	git merge --no-commit side &&
+	test -f .git/MERGE_HEAD &&
+	git merge --abort &&
+	test "$head" = "$(git rev-parse HEAD)" &&
+	test -z "$(git diff HEAD)" &&
+	test ! -f .git/MERGE_HEAD
+'
+
+
+
+test_done
+
+test_expect_success 'merge local branch' '
+	test_commit master-1 &&
+	git checkout -b local-branch &&
+	test_commit branch-1 &&
+	git checkout master &&
+	test_commit master-2 &&
+	git merge local-branch &&
+	check_oneline "Merge branch Qlocal-branchQ"
+'
+
+test_expect_success 'merge octopus branches' '
+	git checkout -b octopus-a master &&
+	test_commit octopus-1 &&
+	git checkout -b octopus-b master &&
+	test_commit octopus-2 &&
+	git checkout master &&
+	git merge octopus-a octopus-b &&
+	check_oneline "Merge branches Qoctopus-aQ and Qoctopus-bQ"
+'
+
+test_expect_success 'merge tag' '
+	git checkout -b tag-branch master &&
+	test_commit tag-1 &&
+	git checkout master &&
+	test_commit master-3 &&
+	git merge tag-1 &&
+	check_oneline "Merge commit Qtag-1Q"
+'
+
+test_expect_success 'ambiguous tag' '
+	git checkout -b ambiguous master &&
+	test_commit ambiguous &&
+	git checkout master &&
+	test_commit master-4 &&
+	git merge ambiguous &&
+	check_oneline "Merge commit QambiguousQ"
+'
+
+test_expect_success 'remote branch' '
+	git checkout -b remote master &&
+	test_commit remote-1 &&
+	git update-ref refs/remotes/origin/master remote &&
+	git checkout master &&
+	test_commit master-5 &&
+	git merge origin/master &&
+	check_oneline "Merge remote branch Qorigin/masterQ"
+'
+
+test_done
-- 
1.7.3.98.g5ad7d9

[PATCHv5 23/23] Provide 'git merge --abort' as a synonym to 'git reset --merge'

[Johan Herland]

Teach 'git merge' the --abort option, which verifies the existence of
MERGE_HEAD and then invokes 'git reset --merge' to abort the current
in-progress merge and attempt to reconstruct the pre-merge state.

The reason for adding this option is to provide a user interface for
aborting an in-progress merge that is consistent with the interface
for aborting a rebase ('git rebase --abort'), aborting the application
of a patch series ('git am --abort'), and aborting an in-progress notes
merge ('git notes merge --abort').

The patch includes documentation and testcases that explain and verify
the various scenarios in which 'git merge --abort' can run. The
testcases also document the cases in which 'git merge --abort' is
unable to correctly restore the pre-merge state (look for the '###'
comments towards the bottom of t/t7609-merge-abort.sh).

Signed-off-by: Johan Herland <johan@herland.net>
---
 Documentation/git-merge.txt |   29 ++++-
 builtin/merge.c             |   14 ++
 t/t7609-merge-abort.sh      |  290 ++++++++++++++++++++++++++++++++++---------
 3 files changed, 273 insertions(+), 60 deletions(-)

diff --git a/Documentation/git-merge.txt b/Documentation/git-merge.txt
index 84043cc..d0099d3 100644
--- a/Documentation/git-merge.txt
+++ b/Documentation/git-merge.txt
@@ -13,6 +13,7 @@ SYNOPSIS
 	[-s <strategy>] [-X <strategy-option>]
 	[--[no-]rerere-autoupdate] [-m <msg>] <commit>...
 'git merge' <msg> HEAD <commit>...
+'git merge' --abort
 
 DESCRIPTION
 -----------
@@ -47,6 +48,15 @@ The second syntax (<msg> `HEAD` <commit>...) is supported for
 historical reasons.  Do not use it from the command line or in
 new scripts.  It is the same as `git merge -m <msg> <commit>...`.
 
+The third syntax ("`git merge --abort`") can only be run after the
+merge has resulted in conflicts. 'git merge --abort' will abort the
+merge process and reconstruct the pre-merge state. However, if there
+were uncommitted changes when the merge started (and these changes
+did not interfere with the merge itself, otherwise the merge would
+have refused to start), and then additional modifications were made
+to these uncommitted changes, 'git merge --abort' will not be able
+reconstruct the original (pre-merge) uncommitted changes. Therefore:
+
 *Warning*: Running 'git merge' with uncommitted changes is
 discouraged: while possible, it leaves you in a state that is hard to
 back out of in the case of a conflict.
@@ -72,6 +82,19 @@ include::merge-options.txt[]
 	Allow the rerere mechanism to update the index with the
 	result of auto-conflict resolution if possible.
 
+--abort::
+	Abort the current conflict resolution process, and
+	reconstruct the pre-merge state.
++
+Any uncommitted worktree changes present when the merge started,
+will only be preserved if they have not been further modified
+since the merge started. Otherwise, git is unable to reconstruct
+uncommitted changes. It is therefore recommended to always commit
+or stash your changes before running 'git merge'.
++
+'git merge --abort' is equivalent to 'git reset --merge' when
+`MERGE_HEAD` is present.
+
 <commit>...::
 	Commits, usually other branch heads, to merge into our branch.
 	You need at least one <commit>.  Specifying more than one
@@ -142,7 +165,7 @@ happens:
    i.e. matching `HEAD`.
 
 If you tried a merge which resulted in complex conflicts and
-want to start over, you can recover with `git reset --merge`.
+want to start over, you can recover with `git merge --abort`.
 
 HOW CONFLICTS ARE PRESENTED
 ---------------------------
@@ -213,8 +236,8 @@ After seeing a conflict, you can do two things:
 
  * Decide not to merge.  The only clean-ups you need are to reset
    the index file to the `HEAD` commit to reverse 2. and to clean
-   up working tree changes made by 2. and 3.; `git-reset --hard` can
-   be used for this.
+   up working tree changes made by 2. and 3.; `git merge --abort`
+   can be used for this.
 
  * Resolve the conflicts.  Git will mark the conflicts in
    the working tree.  Edit the files into shape and
diff --git a/builtin/merge.c b/builtin/merge.c
index 702f399..fbe342f 100644
--- a/builtin/merge.c
+++ b/builtin/merge.c
@@ -56,6 +56,7 @@ static size_t xopts_nr, xopts_alloc;
 static const char *branch;
 static int verbosity;
 static int allow_rerere_auto;
+static int abort_current_merge;
 
 static struct strategy all_strategy[] = {
 	{ "recursive",  DEFAULT_TWOHEAD | NO_TRIVIAL },
@@ -194,6 +195,8 @@ static struct option builtin_merge_options[] = {
 		"message to be used for the merge commit (if any)",
 		option_parse_message),
 	OPT__VERBOSITY(&verbosity),
+	OPT_BOOLEAN(0, "abort", &abort_current_merge,
+		"abort the current in-progress merge"),
 	OPT_END()
 };
 
@@ -914,6 +917,17 @@ int cmd_merge(int argc, const char **argv, const char *prefix)
 	argc = parse_options(argc, argv, prefix, builtin_merge_options,
 			builtin_merge_usage, 0);
 
+	if (abort_current_merge) {
+		int nargc = 2;
+		const char *nargv[] = {"reset", "--merge", NULL};
+
+		if (!file_exists(git_path("MERGE_HEAD")))
+			die("There is no merge to abort (MERGE_HEAD missing).");
+
+		/* Invoke 'git reset --merge' */
+		return cmd_reset(nargc, nargv, prefix);
+	}
+
 	if (read_cache_unmerged()) {
 		die_resolve_conflict("merge");
 	}
diff --git a/t/t7609-merge-abort.sh b/t/t7609-merge-abort.sh
index 88d76e1..011a4c0 100755
--- a/t/t7609-merge-abort.sh
+++ b/t/t7609-merge-abort.sh
@@ -3,95 +3,271 @@
 test_description='test aborting in-progress merges'
 . ./test-lib.sh
 
+# Set up repo with conflicting and non-conflicting branches:
+#
+# master1---master2---foo_foo  <-- master
+#        \
+#         --clean1             <-- clean_branch
+#                 \
+#                  --foo_bar   <-- conflict_branch
+
+test_expect_success 'setup' '
+	test_commit master1 &&
+	git checkout -b clean_branch &&
+	test_commit clean1 &&
+	git checkout -b conflict_branch &&
+	echo bar > foo &&
+	git add foo &&
+	git commit -m "foo_bar" &&
+	git tag foo_bar &&
+	git checkout master &&
+	test_commit master2 &&
+	echo foo > foo &&
+	git add foo &&
+	git commit -m "foo_foo" &&
+	git tag foo_foo
+'
+
 # Test git merge --abort with the following variables:
 # - before/after successful merge (i.e. should fail if not in merge context)
 # - with/without conflicts
+# - clean/dirty index before merge (merge fails on dirty index)
 # - clean/dirty worktree before merge (may fail to reconstruct dirty worktree)
-# - clean/dirty index before merge (merge should fail on dirty index)
+# - dirty worktree before merge matches contents on remote branch
 # - changed/unchanged worktree after merge
 # - changed/unchanged index after merge
 
-test_done
+pre_merge_head="$(git rev-parse HEAD)"
 
 test_expect_success 'fails without MERGE_HEAD (unstarted merge)' '
 	test_must_fail git merge --abort 2>output &&
-	grep -q MERGE_HEAD output
+	grep -q MERGE_HEAD output &&
+	test ! -f .git/MERGE_HEAD &&
+	test "$pre_merge_head" = "$(git rev-parse HEAD)"
 '
 
 test_expect_success 'fails without MERGE_HEAD (completed merge)' '
-	test_commit master-1 &&
-	test_commit master-2 &&
-	git checkout -b side HEAD^ &&
-	test_commit side-1 &&
-	git checkout master &&
-	git merge side &&
+	git merge clean_branch &&
+	test ! -f .git/MERGE_HEAD &&
 	# Merge successfully completed
+	post_merge_head="$(git rev-parse HEAD)" &&
 	test_must_fail git merge --abort 2>output &&
-	grep -q MERGE_HEAD output
+	grep -q MERGE_HEAD output &&
+	test ! -f .git/MERGE_HEAD &&
+	test "$post_merge_head" = "$(git rev-parse HEAD)"
 '
 
-test_expect_success 'Abort successfully after --no-commit' '
-	# Forget previous merge
-	git reset --hard master^ &&
-	head=$(git rev-parse HEAD) &&
-	git merge --no-commit side &&
+test_expect_success 'Forget previous merge' '
+	git reset --hard "$pre_merge_head"
+'
+
+test_expect_success 'Abort after --no-commit' '
+	# Redo merge, but stop before creating merge commit
+	git merge --no-commit clean_branch &&
 	test -f .git/MERGE_HEAD &&
+	# Abort non-conflicting merge
 	git merge --abort &&
-	test "$head" = "$(git rev-parse HEAD)" &&
-	test -z "$(git diff HEAD)" &&
-	test ! -f .git/MERGE_HEAD
+	test ! -f .git/MERGE_HEAD &&
+	test "$pre_merge_head" = "$(git rev-parse HEAD)" &&
+	test -z "$(git diff)" &&
+	test -z "$(git diff --staged)"
 '
 
+test_expect_success 'Abort after conflicts' '
+	# Create conflicting merge
+	test_must_fail git merge conflict_branch &&
+	test -f .git/MERGE_HEAD &&
+	# Abort conflicting merge
+	git merge --abort &&
+	test ! -f .git/MERGE_HEAD &&
+	test "$pre_merge_head" = "$(git rev-parse HEAD)" &&
+	test -z "$(git diff)" &&
+	test -z "$(git diff --staged)"
+'
 
+test_expect_success 'Clean merge with dirty index fails' '
+	echo xyzzy >> foo &&
+	git add foo &&
+	git diff --staged > expect &&
+	test_must_fail git merge clean_branch &&
+	test ! -f .git/MERGE_HEAD &&
+	test "$pre_merge_head" = "$(git rev-parse HEAD)" &&
+	test -z "$(git diff)" &&
+	git diff --staged > actual &&
+	test_cmp expect actual
+'
 
-test_done
+test_expect_success 'Conflicting merge with dirty index fails' '
+	test_must_fail git merge conflict_branch &&
+	test ! -f .git/MERGE_HEAD &&
+	test "$pre_merge_head" = "$(git rev-parse HEAD)" &&
+	test -z "$(git diff)" &&
+	git diff --staged > actual &&
+	test_cmp expect actual
+'
 
-test_expect_success 'merge local branch' '
-	test_commit master-1 &&
-	git checkout -b local-branch &&
-	test_commit branch-1 &&
-	git checkout master &&
-	test_commit master-2 &&
-	git merge local-branch &&
-	check_oneline "Merge branch Qlocal-branchQ"
+test_expect_success 'Reset index (but preserve worktree changes)' '
+	git reset "$pre_merge_head" &&
+	git diff > actual &&
+	test_cmp expect actual
 '
 
-test_expect_success 'merge octopus branches' '
-	git checkout -b octopus-a master &&
-	test_commit octopus-1 &&
-	git checkout -b octopus-b master &&
-	test_commit octopus-2 &&
-	git checkout master &&
-	git merge octopus-a octopus-b &&
-	check_oneline "Merge branches Qoctopus-aQ and Qoctopus-bQ"
+test_expect_success 'Abort clean merge with non-conflicting dirty worktree' '
+	git merge --no-commit clean_branch &&
+	test -f .git/MERGE_HEAD &&
+	# Abort merge
+	git merge --abort &&
+	test ! -f .git/MERGE_HEAD &&
+	test "$pre_merge_head" = "$(git rev-parse HEAD)" &&
+	test -z "$(git diff --staged)" &&
+	git diff > actual &&
+	test_cmp expect actual
 '
 
-test_expect_success 'merge tag' '
-	git checkout -b tag-branch master &&
-	test_commit tag-1 &&
-	git checkout master &&
-	test_commit master-3 &&
-	git merge tag-1 &&
-	check_oneline "Merge commit Qtag-1Q"
+test_expect_success 'Reset worktree changes' '
+	git reset --hard "$pre_merge_head" &&
+	git clean -f
 '
 
-test_expect_success 'ambiguous tag' '
-	git checkout -b ambiguous master &&
-	test_commit ambiguous &&
-	git checkout master &&
-	test_commit master-4 &&
-	git merge ambiguous &&
-	check_oneline "Merge commit QambiguousQ"
+test_expect_success 'Abort conflicting merge with non-conflicting dirty worktree' '
+	echo xyzzy >> master1.t &&
+	git diff > expect &&
+	test_must_fail git merge conflict_branch &&
+	test -f .git/MERGE_HEAD &&
+	# Abort merge
+	git merge --abort &&
+	test ! -f .git/MERGE_HEAD &&
+	test "$pre_merge_head" = "$(git rev-parse HEAD)" &&
+	test -z "$(git diff --staged)" &&
+	git diff > actual &&
+	test_cmp expect actual
 '
 
-test_expect_success 'remote branch' '
-	git checkout -b remote master &&
-	test_commit remote-1 &&
-	git update-ref refs/remotes/origin/master remote &&
-	git checkout master &&
-	test_commit master-5 &&
-	git merge origin/master &&
-	check_oneline "Merge remote branch Qorigin/masterQ"
+test_expect_success 'Reset worktree changes' '
+	git reset --hard "$pre_merge_head" &&
+	git clean -f
+'
+
+test_expect_success 'Fail clean merge with conflicting dirty worktree' '
+	echo xyzzy >> clean1.t &&
+	git diff > expect &&
+	test_must_fail git merge --no-commit clean_branch &&
+	test ! -f .git/MERGE_HEAD &&
+	test "$pre_merge_head" = "$(git rev-parse HEAD)" &&
+	test -z "$(git diff --staged)" &&
+	git diff > actual &&
+	test_cmp expect actual
+'
+
+test_expect_success 'Reset worktree changes' '
+	git reset --hard "$pre_merge_head" &&
+	git clean -f
+'
+
+test_expect_success 'Fail clean merge with matching dirty worktree' '
+	echo clean1 > clean1.t &&
+	git diff > expect &&
+	test_must_fail git merge --no-commit clean_branch &&
+	test ! -f .git/MERGE_HEAD &&
+	test "$pre_merge_head" = "$(git rev-parse HEAD)" &&
+	test -z "$(git diff --staged)" &&
+	git diff > actual &&
+	test_cmp expect actual
+'
+
+test_expect_success 'Reset worktree changes' '
+	git reset --hard "$pre_merge_head" &&
+	git clean -f
+'
+
+test_expect_success 'Fail conflicting merge with conflicting dirty worktree' '
+	echo xyzzy >> foo &&
+	git diff > expect &&
+	test_must_fail git merge conflict_branch &&
+	test ! -f .git/MERGE_HEAD &&
+	test "$pre_merge_head" = "$(git rev-parse HEAD)" &&
+	test -z "$(git diff --staged)" &&
+	git diff > actual &&
+	test_cmp expect actual
+'
+test_expect_success 'Reset worktree changes' '
+	git reset --hard "$pre_merge_head" &&
+	git clean -f
+'
+
+test_expect_success 'Fail conflicting merge with matching dirty worktree' '
+	echo bar > foo &&
+	git diff > expect &&
+	test_must_fail git merge conflict_branch &&
+	test ! -f .git/MERGE_HEAD &&
+	test "$pre_merge_head" = "$(git rev-parse HEAD)" &&
+	test -z "$(git diff --staged)" &&
+	git diff > actual &&
+	test_cmp expect actual
+'
+
+test_expect_success 'Reset worktree changes' '
+	git reset --hard "$pre_merge_head" &&
+	git clean -f
+'
+
+test_expect_success 'Abort merge with pre- and post-merge worktree changes' '
+	# Pre-merge worktree changes
+	echo xyzzy >> master1.t &&
+	git diff > expect &&
+	# Perform merge
+	test_must_fail git merge conflict_branch &&
+	test -f .git/MERGE_HEAD &&
+	# Post-merge worktree changes
+	echo barf >> master1.t &&
+	echo barf > foo &&
+	### When aborting the merge, git can reconstruct foo, but for non-
+	### conflicting files it cannot tell pre-merge changes apart from
+	### post-merge changes. Therefore, the master1.t file will reflect
+	### the post-merge state, while the foo file will reflect the
+	### pre-merge (unchanged) state. Change expectations accordingly:
+	git diff master1.t > expect &&
+	# Abort merge
+	git merge --abort &&
+	test ! -f .git/MERGE_HEAD &&
+	test "$pre_merge_head" = "$(git rev-parse HEAD)" &&
+	test -z "$(git diff --staged)" &&
+	git diff > actual &&
+	test_cmp expect actual
+'
+
+test_expect_success 'Reset worktree changes' '
+	git reset --hard "$pre_merge_head" &&
+	git clean -f
+'
+
+test_expect_success 'Abort merge with pre-merge worktree changes and post-merge index changes' '
+	# Pre-merge worktree changes
+	echo xyzzy >> master1.t &&
+	echo xyzzy >> master2.t &&
+	### See explanation below for why we only expect the diff of master2.t
+	git diff master2.t > expect &&
+	# Perform merge
+	test_must_fail git merge conflict_branch &&
+	test -f .git/MERGE_HEAD &&
+	# Post-merge worktree changes
+	echo barf >> master1.t &&
+	echo barf > foo &&
+	git add master1.t foo &&
+	### When aborting the merge, git will remove all staged changes,
+	### including those that were staged post-merge. For any post-merge
+	### changes that have overwritten pre-merge changes, git cannot
+	### reconstruct the pre-merge changes. In this scenario, foo and
+	### master1.t are reset to a clean state (i.e. losing the pre-merge
+	### changes in master1.t), but the pre-merge changes in master2.t are
+	### preserved (since it was not changed post-merge).
+	# Abort merge
+	git merge --abort &&
+	test ! -f .git/MERGE_HEAD &&
+	test "$pre_merge_head" = "$(git rev-parse HEAD)" &&
+	test -z "$(git diff --staged)" &&
+	git diff > actual &&
+	test_cmp expect actual
 '
 
 test_done
-- 
1.7.3.98.g5ad7d9

Re: [PATCHv5 23/23] Provide 'git merge --abort' as a synonym to 'git reset --merge'

[Jonathan Nieder]

Johan Herland wrote:

> --- a/Documentation/git-merge.txt
> +++ b/Documentation/git-merge.txt
> @@ -13,6 +13,7 @@ SYNOPSIS
>                                                     However, if there
> +were uncommitted changes when the merge started (and these changes
> +did not interfere with the merge itself, otherwise the merge would
> +have refused to start), and then additional modifications were made
> +to these uncommitted changes, 'git merge --abort' will not be able
> +reconstruct the original (pre-merge) uncommitted changes. Therefore:

I do not find this clear.  Could you give an example?

References:

 http://thread.gmane.org/gmane.comp.version-control.git/136356/focus=136773
 http://thread.gmane.org/gmane.comp.version-control.git/151799/focus=151812

> +--abort::
> +	Abort the current conflict resolution process, and
> +	reconstruct the pre-merge state.
> ++
> +Any uncommitted worktree changes present when the merge started,
> +will only be preserved if they have not been further modified
> +since the merge started.

Ah, maybe I see: is the problem this procedure?

 1. Make changes to file foo.c (without staging them).
 2. Try a merge (which cannot touch foo.c, or the merge would have
    been aborted automatically) which fails with conflicts.
 3. As a result of semantic conflicts, make some changes to foo.c.
 4. Wish to return to the state from the end of step 1.

But I find the following more likely:

 1. Make changes to file foo.c (without staging them).
 2. Try a merge (which cannot touch foo.c, or the merge would have
    been aborted automatically) which fails with conflicts.
 3. Walk away in disgust.
 4. Return, make some more changes to foo.c.
 5. Notice the merge in progress --- oh! --- and abort it.

> --- a/t/t7609-merge-abort.sh
> +++ b/t/t7609-merge-abort.sh
> @@ -3,95 +3,271 @@
>  test_description='test aborting in-progress merges'
>  . ./test-lib.sh
>  
> +# Set up repo with conflicting and non-conflicting branches:
> +#
> +# master1---master2---foo_foo  <-- master
> +#        \
> +#         --clean1             <-- clean_branch
> +#                 \
> +#                  --foo_bar   <-- conflict_branch

[It might be nice to include this in test_description for use by
 "./t7609-merge-abort.sh --help".]

> +# - dirty worktree before merge matches contents on remote branch

Or maybe this was the example.  Here was Junio's explanation of it:

| It will discard the change, the one you independently picked up, but the
| change agreed with what was done by the the trash history that you are
| cancelling merge with.  You wouldn't miss losing the same change as in
| that trash history.

In other words, if the change is also on a remote branch that you want
not to merge with anyway, it is not likely to be terribly important to
preserve it in the local tree.  (This is a trade-off between
convenience in two different scenarios.)

Hope that helps (sorry for the ramble).

Re: [PATCHv5 23/23] Provide 'git merge --abort' as a synonym to 'git reset --merge'

[Johan Herland]

On Monday 25 October 2010, Jonathan Nieder wrote:
> Johan Herland wrote:
> > --- a/Documentation/git-merge.txt
> > +++ b/Documentation/git-merge.txt
> > @@ -13,6 +13,7 @@ SYNOPSIS
> > 
> >                                                     However, if there
> > +were uncommitted changes when the merge started (and these changes
> > +did not interfere with the merge itself, otherwise the merge would
> > +have refused to start), and then additional modifications were made
> > +to these uncommitted changes, 'git merge --abort' will not be able
> > +reconstruct the original (pre-merge) uncommitted changes. Therefore:
>
> I do not find this clear.  Could you give an example?

I'll try. Given these commands:

  git init
  echo foo > foo
  echo bar > bar
  echo baz > baz
  git add foo bar baz
  git commit -m initial
  git checkout -b side
  echo blarg > bar
  echo blazg > baz
  git commit -a -m "side"
  git checkout master
  echo xyzzy > bar
  git commit -a -m "xyzzy"

We now have the following repo, in terms of bar/baz's contents:

  bar/baz---xyzzy/baz    <-- master
         \
          --blarg/blazg  <-- side

Now, before we merge side into master, consider what uncommitted changes we 
can make before starting the merge:

  A. (no changes)

  B. Change foo to something different [echo blech > foo]

  C. Same as (B), plus stage foo [git add foo]

  D. Change bar to something different [echo blech > bar]

  E. Same as (D), plus stage bar [git add bar]

  F. Change baz to something different [echo blech > baz]

  G. Same as (F), plus stage baz [git add baz]

  H. Change baz to "blazg" [echo blazg > baz]

  I. Same as (H), plus stage baz [git add baz]

AFAICS, this is a complete list of pre-merge uncommitted changes we can 
make. Everything else is either uninteresting, or can be classified in terms 
of (a combination of) the above 9 cases.

Now, we can immediately disregard cases (C), (D), (E), (F), (G) and (H), 
since 'git merge' refuses to start merging:

  $ git merge side
  error: Your local changes to the following files would be overwritten by
  merge:
          foo/bar/baz
  Please, commit your changes or stash them before you can merge.
  Aborting

So we're left with considering cases (A), (B) and (I). These cases are 
preserved by the merge, in that:

  A. Non-changes are still non-changes after the merge.

  B. Uncommitted changes are still uncommitted changes.

  I. Staged changes (matching the other branch) are still staged changes.

Now, my experiments in t7609 (although I now see that I have failed to 
properly recreate case (I); this will be fixed in the next iteration) 
demonstrate that 'git merge --abort' will preserve uncommitted changes, and 
discard staged changes. As such cases (A) and (B) will be preserved by 'git 
merge --abort', while case (I) will be lost.

Furthermore, experiments (in t7609) show that 'git merge --abort' is unable 
to identify any changes done after the merge attempt and before 'git merge 
--abort'. As such, if you make any more staged or unstaged changes, they 
will be handled by 'git merge --abort' as though they happened before the 
merge (i.e. unstaged changes are preserved, staged changes are discarded).

I should therefore update the documentation to be a little broader in its 
warning against merging with uncommitted changes. Maybe something like:

  However, if there were uncommitted changes when the merge started,
  'git merge --abort' will in some cases be unable to recreate these
  changes. Especially if further changes were made after the merge was
  started, 'git merge --abort' is unable to reconstruct the original
  (pre-merge) changes. Therefore:

> References:
> 
> http://thread.gmane.org/gmane.comp.version-control.git/136356/focus=136773
> http://thread.gmane.org/gmane.comp.version-control.git/151799/focus=151812

Thanks. I hadn't read those before preparing these. Instead I tried to 
document the current behaviour by testing all scenarios (that I could think 
of) in t7609, and documenting the results, extensively in t7609 and somewhat 
more abbreviated in the man page.

> > +--abort::
> > +	Abort the current conflict resolution process, and
> > +	reconstruct the pre-merge state.
> > ++
> > +Any uncommitted worktree changes present when the merge started,
> > +will only be preserved if they have not been further modified
> > +since the merge started.
> 
> Ah, maybe I see: is the problem this procedure?
> 
>  1. Make changes to file foo.c (without staging them).
>  2. Try a merge (which cannot touch foo.c, or the merge would have
>     been aborted automatically) which fails with conflicts.
>  3. As a result of semantic conflicts, make some changes to foo.c.
>  4. Wish to return to the state from the end of step 1.

Exactly. That's one of the cases presented above.

> But I find the following more likely:
> 
>  1. Make changes to file foo.c (without staging them).
>  2. Try a merge (which cannot touch foo.c, or the merge would have
>     been aborted automatically) which fails with conflicts.
>  3. Walk away in disgust.
>  4. Return, make some more changes to foo.c.
>  5. Notice the merge in progress --- oh! --- and abort it.

Yeah, in that case the current behaviour will actually work for you, as long 
as you DON'T stage your changes (staged + abort => changes lost, d'oh).

> > --- a/t/t7609-merge-abort.sh
> > +++ b/t/t7609-merge-abort.sh
> > @@ -3,95 +3,271 @@
> > 
> >  test_description='test aborting in-progress merges'
> >  . ./test-lib.sh
> > 
> > +# Set up repo with conflicting and non-conflicting branches:
> > +#
> > +# master1---master2---foo_foo  <-- master
> > +#        \
> > +#         --clean1             <-- clean_branch
> > +#                 \
> > +#                  --foo_bar   <-- conflict_branch
> 
> [It might be nice to include this in test_description for use by
>  "./t7609-merge-abort.sh --help".]

Agreed. Will fix.

> > +# - dirty worktree before merge matches contents on remote branch
> 
> Or maybe this was the example.  Here was Junio's explanation of it:
> | It will discard the change, the one you independently picked up, but
> | the change agreed with what was done by the the trash history that you
> | are cancelling merge with.  You wouldn't miss losing the same change
> | as in that trash history.

Yeah, but I've now found that I failed to test that case. Will be fixed in 
the next iteration.

> In other words, if the change is also on a remote branch that you want
> not to merge with anyway, it is not likely to be terribly important to
> preserve it in the local tree.  (This is a trade-off between
> convenience in two different scenarios.)

Yeah, it's an argument that will work in some situations, but not all. Say 
you happend to stage something after the merge, but before you 'git merge --
abort'. That change will be obliterated by the --abort, which is likely not 
what you wanted.

> Hope that helps (sorry for the ramble).

That was _immensely_ helpful, since it cleared my own jumbled thoughts on 
the matter, and identified a missing/miscreated case in t7609. Thanks!


...Johan

-- 
Johan Herland, <johan@herland.net>
www.herland.net

Re: [PATCHv5 23/23] Provide 'git merge --abort' as a synonym to 'git reset --merge'

[Johan Herland]

On Monday 25 October 2010, Johan Herland wrote:
> On Monday 25 October 2010, Jonathan Nieder wrote:
> > Johan Herland wrote:
> > >                                                  However, if there
> > > +were uncommitted changes when the merge started (and these changes
> > > +did not interfere with the merge itself, otherwise the merge would
> > > +have refused to start), and then additional modifications were made
> > > +to these uncommitted changes, 'git merge --abort' will not be able
> > 
> > > +reconstruct the original (pre-merge) uncommitted changes. Therefore:
> > I do not find this clear.  Could you give an example?

[...]

> > > +# - dirty worktree before merge matches contents on remote branch
> > 
> > Or maybe this was the example.  Here was Junio's explanation of it:
> > | It will discard the change, the one you independently picked up, but
> > | the change agreed with what was done by the the trash history that
> > | you are cancelling merge with.  You wouldn't miss losing the same
> > | change as in that trash history.
> 
> Yeah, but I've now found that I failed to test that case. Will be fixed
> in the next iteration.

Instead of sending an entire new patch series when I've only changed the 
last two patches, I'm gonna send only those two patches, marked "PATCHv5.1", 
as a reply to this email.


Hope this is ok,

...Johan

-- 
Johan Herland, <johan@herland.net>
www.herland.net

[PATCHv5.1 22/23] cmd_merge(): Parse options before checking MERGE_HEAD

[Johan Herland]

Reorder the initial part of builtin/merge.c:cmd_merge() so that command-line
options are parsed _before_ we load the index and check for MERGE_HEAD
(and exits if it exists). This does not change the behaviour of 'git merge',
but is needed in preparation for the implementation of 'git merge --abort'
(which requires MERGE_HEAD to be present).

Signed-off-by: Johan Herland <johan@herland.net>
---

In the previous version of this patch, I somehow managed to misplace
parts of t7609 here instead of in the next commit. Fixed now.

Otherwise, no changes.


...Johan

 builtin/merge.c |   33 +++++++++++++++++----------------
 1 files changed, 17 insertions(+), 16 deletions(-)

diff --git a/builtin/merge.c b/builtin/merge.c
index 37ce4f5..702f399 100644
--- a/builtin/merge.c
+++ b/builtin/merge.c
@@ -895,22 +895,6 @@ int cmd_merge(int argc, const char **argv, const char *prefix)
 	const char *best_strategy = NULL, *wt_strategy = NULL;
 	struct commit_list **remotes = &remoteheads;
 
-	if (read_cache_unmerged()) {
-		die_resolve_conflict("merge");
-	}
-	if (file_exists(git_path("MERGE_HEAD"))) {
-		/*
-		 * There is no unmerged entry, don't advise 'git
-		 * add/rm <file>', just 'git commit'.
-		 */
-		if (advice_resolve_conflict)
-			die("You have not concluded your merge (MERGE_HEAD exists).\n"
-			    "Please, commit your changes before you can merge.");
-		else
-			die("You have not concluded your merge (MERGE_HEAD exists).");
-	}
-
-	resolve_undo_clear();
 	/*
 	 * Check if we are _not_ on a detached HEAD, i.e. if there is a
 	 * current branch.
@@ -929,6 +913,23 @@ int cmd_merge(int argc, const char **argv, const char *prefix)
 
 	argc = parse_options(argc, argv, prefix, builtin_merge_options,
 			builtin_merge_usage, 0);
+
+	if (read_cache_unmerged()) {
+		die_resolve_conflict("merge");
+	}
+	if (file_exists(git_path("MERGE_HEAD"))) {
+		/*
+		 * There is no unmerged entry, don't advise 'git
+		 * add/rm <file>', just 'git commit'.
+		 */
+		if (advice_resolve_conflict)
+			die("You have not concluded your merge (MERGE_HEAD exists).\n"
+			    "Please, commit your changes before you can merge.");
+		else
+			die("You have not concluded your merge (MERGE_HEAD exists).");
+	}
+	resolve_undo_clear();
+
 	if (verbosity < 0)
 		show_diffstat = 0;
 
-- 
1.7.3.2.173.gab1c9.dirty

[PATCHv5.1 23/23] Provide 'git merge --abort' as a synonym to 'git reset --merge'

[Johan Herland]

Teach 'git merge' the --abort option, which verifies the existence of
MERGE_HEAD and then invokes 'git reset --merge' to abort the current
in-progress merge and attempt to reconstruct the pre-merge state.

The reason for adding this option is to provide a user interface for
aborting an in-progress merge that is consistent with the interface
for aborting a rebase ('git rebase --abort'), aborting the application
of a patch series ('git am --abort'), and aborting an in-progress notes
merge ('git notes merge --abort').

The patch includes documentation and testcases that explain and verify
the various scenarios in which 'git merge --abort' can run. The
testcases also document the cases in which 'git merge --abort' is
unable to correctly restore the pre-merge state (look for the '###'
comments towards the bottom of t/t7609-merge-abort.sh).

This patch has been improved by the following contributions:
- Jonathan Nieder: Move test documentation into test_description

Thanks-to: Jonathan Nieder <jrnieder@gmail.com>
Signed-off-by: Johan Herland <johan@herland.net>
---

Hi,

The documentation and test cases in this patch has been extensively
updated. The code in builtin/merge.s is unchanged.

Again, thanks to Jonathan Nieder for extremely helpful reviews.


Have fun! :)

...Johan

 Documentation/git-merge.txt |   27 ++++-
 builtin/merge.c             |   14 ++
 t/t7609-merge-abort.sh      |  313 +++++++++++++++++++++++++++++++++++++++++++
 3 files changed, 351 insertions(+), 3 deletions(-)
 create mode 100755 t/t7609-merge-abort.sh

diff --git a/Documentation/git-merge.txt b/Documentation/git-merge.txt
index 84043cc..47b59a5 100644
--- a/Documentation/git-merge.txt
+++ b/Documentation/git-merge.txt
@@ -13,6 +13,7 @@ SYNOPSIS
 	[-s <strategy>] [-X <strategy-option>]
 	[--[no-]rerere-autoupdate] [-m <msg>] <commit>...
 'git merge' <msg> HEAD <commit>...
+'git merge' --abort
 
 DESCRIPTION
 -----------
@@ -47,6 +48,14 @@ The second syntax (<msg> `HEAD` <commit>...) is supported for
 historical reasons.  Do not use it from the command line or in
 new scripts.  It is the same as `git merge -m <msg> <commit>...`.
 
+The third syntax ("`git merge --abort`") can only be run after the
+merge has resulted in conflicts. 'git merge --abort' will abort the
+merge process and try to reconstruct the pre-merge state. However,
+if there were uncommitted changes when the merge started (and
+especially if those changes were further modified after the merge
+was started), 'git merge --abort' will in some cases be unable to
+reconstruct the original (pre-merge) changes. Therefore:
+
 *Warning*: Running 'git merge' with uncommitted changes is
 discouraged: while possible, it leaves you in a state that is hard to
 back out of in the case of a conflict.
@@ -72,6 +81,18 @@ include::merge-options.txt[]
 	Allow the rerere mechanism to update the index with the
 	result of auto-conflict resolution if possible.
 
+--abort::
+	Abort the current conflict resolution process, and
+	try to reconstruct the pre-merge state.
++
+If there were uncommitted worktree changes present when the merge
+started, 'git merge --abort' will in some cases be unable to
+reconstruct these changes. It is therefore recommended to always
+commit or stash your changes before running 'git merge'.
++
+'git merge --abort' is equivalent to 'git reset --merge' when
+`MERGE_HEAD` is present.
+
 <commit>...::
 	Commits, usually other branch heads, to merge into our branch.
 	You need at least one <commit>.  Specifying more than one
@@ -142,7 +163,7 @@ happens:
    i.e. matching `HEAD`.
 
 If you tried a merge which resulted in complex conflicts and
-want to start over, you can recover with `git reset --merge`.
+want to start over, you can recover with `git merge --abort`.
 
 HOW CONFLICTS ARE PRESENTED
 ---------------------------
@@ -213,8 +234,8 @@ After seeing a conflict, you can do two things:
 
  * Decide not to merge.  The only clean-ups you need are to reset
    the index file to the `HEAD` commit to reverse 2. and to clean
-   up working tree changes made by 2. and 3.; `git-reset --hard` can
-   be used for this.
+   up working tree changes made by 2. and 3.; `git merge --abort`
+   can be used for this.
 
  * Resolve the conflicts.  Git will mark the conflicts in
    the working tree.  Edit the files into shape and
diff --git a/builtin/merge.c b/builtin/merge.c
index 702f399..fbe342f 100644
--- a/builtin/merge.c
+++ b/builtin/merge.c
@@ -56,6 +56,7 @@ static size_t xopts_nr, xopts_alloc;
 static const char *branch;
 static int verbosity;
 static int allow_rerere_auto;
+static int abort_current_merge;
 
 static struct strategy all_strategy[] = {
 	{ "recursive",  DEFAULT_TWOHEAD | NO_TRIVIAL },
@@ -194,6 +195,8 @@ static struct option builtin_merge_options[] = {
 		"message to be used for the merge commit (if any)",
 		option_parse_message),
 	OPT__VERBOSITY(&verbosity),
+	OPT_BOOLEAN(0, "abort", &abort_current_merge,
+		"abort the current in-progress merge"),
 	OPT_END()
 };
 
@@ -914,6 +917,17 @@ int cmd_merge(int argc, const char **argv, const char *prefix)
 	argc = parse_options(argc, argv, prefix, builtin_merge_options,
 			builtin_merge_usage, 0);
 
+	if (abort_current_merge) {
+		int nargc = 2;
+		const char *nargv[] = {"reset", "--merge", NULL};
+
+		if (!file_exists(git_path("MERGE_HEAD")))
+			die("There is no merge to abort (MERGE_HEAD missing).");
+
+		/* Invoke 'git reset --merge' */
+		return cmd_reset(nargc, nargv, prefix);
+	}
+
 	if (read_cache_unmerged()) {
 		die_resolve_conflict("merge");
 	}
diff --git a/t/t7609-merge-abort.sh b/t/t7609-merge-abort.sh
new file mode 100755
index 0000000..61890bc
--- /dev/null
+++ b/t/t7609-merge-abort.sh
@@ -0,0 +1,313 @@
+#!/bin/sh
+
+test_description='test aborting in-progress merges
+
+Set up repo with conflicting and non-conflicting branches:
+
+There are three files foo/bar/baz, and the following graph illustrates the
+content of these files in each commit:
+
+# foo/bar/baz --- foo/bar/bazz     <-- master
+#             \
+#              --- foo/barf/bazf   <-- conflict_branch
+#               \
+#                --- foo/bart/baz  <-- clean_branch
+
+Next, test git merge --abort with the following variables:
+- before/after successful merge (should fail when not in merge context)
+- with/without conflicts
+- clean/dirty index before merge
+- clean/dirty worktree before merge
+- dirty index before merge matches contents on remote branch
+- changed/unchanged worktree after merge
+- changed/unchanged index after merge
+'
+. ./test-lib.sh
+
+test_expect_success 'setup' '
+	# Create the above repo
+	echo foo > foo &&
+	echo bar > bar &&
+	echo baz > baz &&
+	git add foo bar baz &&
+	git commit -m initial &&
+	echo bazz > baz &&
+	git commit -a -m "second" &&
+	git checkout -b conflict_branch HEAD^ &&
+	echo barf > bar &&
+	echo bazf > baz &&
+	git commit -a -m "conflict" &&
+	git checkout -b clean_branch HEAD^ &&
+	echo bart > bar &&
+	git commit -a -m "clean" &&
+	git checkout master
+'
+
+pre_merge_head="$(git rev-parse HEAD)"
+
+test_expect_success 'fails without MERGE_HEAD (unstarted merge)' '
+	test_must_fail git merge --abort 2>output &&
+	grep -q MERGE_HEAD output &&
+	test ! -f .git/MERGE_HEAD &&
+	test "$pre_merge_head" = "$(git rev-parse HEAD)"
+'
+
+test_expect_success 'fails without MERGE_HEAD (completed merge)' '
+	git merge clean_branch &&
+	test ! -f .git/MERGE_HEAD &&
+	# Merge successfully completed
+	post_merge_head="$(git rev-parse HEAD)" &&
+	test_must_fail git merge --abort 2>output &&
+	grep -q MERGE_HEAD output &&
+	test ! -f .git/MERGE_HEAD &&
+	test "$post_merge_head" = "$(git rev-parse HEAD)"
+'
+
+test_expect_success 'Forget previous merge' '
+	git reset --hard "$pre_merge_head"
+'
+
+test_expect_success 'Abort after --no-commit' '
+	# Redo merge, but stop before creating merge commit
+	git merge --no-commit clean_branch &&
+	test -f .git/MERGE_HEAD &&
+	# Abort non-conflicting merge
+	git merge --abort &&
+	test ! -f .git/MERGE_HEAD &&
+	test "$pre_merge_head" = "$(git rev-parse HEAD)" &&
+	test -z "$(git diff)" &&
+	test -z "$(git diff --staged)"
+'
+
+test_expect_success 'Abort after conflicts' '
+	# Create conflicting merge
+	test_must_fail git merge conflict_branch &&
+	test -f .git/MERGE_HEAD &&
+	# Abort conflicting merge
+	git merge --abort &&
+	test ! -f .git/MERGE_HEAD &&
+	test "$pre_merge_head" = "$(git rev-parse HEAD)" &&
+	test -z "$(git diff)" &&
+	test -z "$(git diff --staged)"
+'
+
+test_expect_success 'Clean merge with dirty index fails' '
+	echo xyzzy >> foo &&
+	git add foo &&
+	git diff --staged > expect &&
+	test_must_fail git merge clean_branch &&
+	test ! -f .git/MERGE_HEAD &&
+	test "$pre_merge_head" = "$(git rev-parse HEAD)" &&
+	test -z "$(git diff)" &&
+	git diff --staged > actual &&
+	test_cmp expect actual
+'
+
+test_expect_success 'Conflicting merge with dirty index fails' '
+	test_must_fail git merge conflict_branch &&
+	test ! -f .git/MERGE_HEAD &&
+	test "$pre_merge_head" = "$(git rev-parse HEAD)" &&
+	test -z "$(git diff)" &&
+	git diff --staged > actual &&
+	test_cmp expect actual
+'
+
+test_expect_success 'Reset index (but preserve worktree changes)' '
+	git reset "$pre_merge_head" &&
+	git diff > actual &&
+	test_cmp expect actual
+'
+
+test_expect_success 'Abort clean merge with non-conflicting dirty worktree' '
+	git merge --no-commit clean_branch &&
+	test -f .git/MERGE_HEAD &&
+	# Abort merge
+	git merge --abort &&
+	test ! -f .git/MERGE_HEAD &&
+	test "$pre_merge_head" = "$(git rev-parse HEAD)" &&
+	test -z "$(git diff --staged)" &&
+	git diff > actual &&
+	test_cmp expect actual
+'
+
+test_expect_success 'Abort conflicting merge with non-conflicting dirty worktree' '
+	test_must_fail git merge conflict_branch &&
+	test -f .git/MERGE_HEAD &&
+	# Abort merge
+	git merge --abort &&
+	test ! -f .git/MERGE_HEAD &&
+	test "$pre_merge_head" = "$(git rev-parse HEAD)" &&
+	test -z "$(git diff --staged)" &&
+	git diff > actual &&
+	test_cmp expect actual
+'
+
+test_expect_success 'Reset worktree changes' '
+	git reset --hard "$pre_merge_head"
+'
+
+test_expect_success 'Fail clean merge with conflicting dirty worktree' '
+	echo xyzzy >> bar &&
+	git diff > expect &&
+	test_must_fail git merge --no-commit clean_branch &&
+	test ! -f .git/MERGE_HEAD &&
+	test "$pre_merge_head" = "$(git rev-parse HEAD)" &&
+	test -z "$(git diff --staged)" &&
+	git diff > actual &&
+	test_cmp expect actual
+'
+
+test_expect_success 'Fail conflicting merge with conflicting dirty worktree' '
+	test_must_fail git merge conflict_branch &&
+	test ! -f .git/MERGE_HEAD &&
+	test "$pre_merge_head" = "$(git rev-parse HEAD)" &&
+	test -z "$(git diff --staged)" &&
+	git diff > actual &&
+	test_cmp expect actual
+'
+
+test_expect_success 'Reset worktree changes' '
+	git reset --hard "$pre_merge_head"
+'
+
+test_expect_success 'Fail clean merge with matching dirty worktree' '
+	echo bart > bar &&
+	git diff > expect &&
+	test_must_fail git merge --no-commit clean_branch &&
+	test ! -f .git/MERGE_HEAD &&
+	test "$pre_merge_head" = "$(git rev-parse HEAD)" &&
+	test -z "$(git diff --staged)" &&
+	git diff > actual &&
+	test_cmp expect actual
+'
+
+test_expect_success 'Abort clean merge with matching dirty index' '
+	git add bar &&
+	git diff --staged > expect &&
+	git merge --no-commit clean_branch &&
+	test -f .git/MERGE_HEAD &&
+	### When aborting the merge, git will discard all staged changes,
+	### including those that were staged pre-merge. In other words,
+	### --abort will LOSE any staged changes (the staged changes that
+	### are lost must match the merge result, or the merge would not
+	### have been allowed to start). Change expectations accordingly:
+	rm expect &&
+	touch expect &&
+	# Abort merge
+	git merge --abort &&
+	test ! -f .git/MERGE_HEAD &&
+	test "$pre_merge_head" = "$(git rev-parse HEAD)" &&
+	git diff --staged > actual &&
+	test_cmp expect actual &&
+	test -z "$(git diff)"
+'
+
+test_expect_success 'Reset worktree changes' '
+	git reset --hard "$pre_merge_head"
+'
+
+test_expect_success 'Fail conflicting merge with matching dirty worktree' '
+	echo barf > bar &&
+	git diff > expect &&
+	test_must_fail git merge conflict_branch &&
+	test ! -f .git/MERGE_HEAD &&
+	test "$pre_merge_head" = "$(git rev-parse HEAD)" &&
+	test -z "$(git diff --staged)" &&
+	git diff > actual &&
+	test_cmp expect actual
+'
+
+test_expect_success 'Abort conflicting merge with matching dirty index' '
+	git add bar &&
+	git diff --staged > expect &&
+	test_must_fail git merge conflict_branch &&
+	test -f .git/MERGE_HEAD &&
+	### When aborting the merge, git will discard all staged changes,
+	### including those that were staged pre-merge. In other words,
+	### --abort will LOSE any staged changes (the staged changes that
+	### are lost must match the merge result, or the merge would not
+	### have been allowed to start). Change expectations accordingly:
+	rm expect &&
+	touch expect &&
+	# Abort merge
+	git merge --abort &&
+	test ! -f .git/MERGE_HEAD &&
+	test "$pre_merge_head" = "$(git rev-parse HEAD)" &&
+	git diff --staged > actual &&
+	test_cmp expect actual &&
+	test -z "$(git diff)"
+'
+
+test_expect_success 'Reset worktree changes' '
+	git reset --hard "$pre_merge_head"
+'
+
+test_expect_success 'Abort merge with pre- and post-merge worktree changes' '
+	# Pre-merge worktree changes
+	echo xyzzy > foo &&
+	echo barf > bar &&
+	git add bar &&
+	git diff > expect &&
+	git diff --staged > expect-staged &&
+	# Perform merge
+	test_must_fail git merge conflict_branch &&
+	test -f .git/MERGE_HEAD &&
+	# Post-merge worktree changes
+	echo yzxxz > foo &&
+	echo blech > baz &&
+	### When aborting the merge, git will discard staged changes (bar)
+	### and unmerged changes (baz). Other changes that are neither
+	### staged nor marked as unmerged (foo), will be preserved. For
+	### these changed, git cannot tell pre-merge changes apart from
+	### post-merge changes, so the post-merge changes will be
+	### preserved. Change expectations accordingly:
+	git diff -- foo > expect &&
+	rm expect-staged &&
+	touch expect-staged &&
+	# Abort merge
+	git merge --abort &&
+	test ! -f .git/MERGE_HEAD &&
+	test "$pre_merge_head" = "$(git rev-parse HEAD)" &&
+	git diff > actual &&
+	test_cmp expect actual &&
+	git diff --staged > actual-staged &&
+	test_cmp expect-staged actual-staged
+'
+
+test_expect_success 'Reset worktree changes' '
+	git reset --hard "$pre_merge_head"
+'
+
+test_expect_success 'Abort merge with pre- and post-merge index changes' '
+	# Pre-merge worktree changes
+	echo xyzzy > foo &&
+	echo barf > bar &&
+	git add bar &&
+	git diff > expect &&
+	git diff --staged > expect-staged &&
+	# Perform merge
+	test_must_fail git merge conflict_branch &&
+	test -f .git/MERGE_HEAD &&
+	# Post-merge worktree changes
+	echo yzxxz > foo &&
+	echo blech > baz &&
+	git add foo bar &&
+	### When aborting the merge, git will discard all staged changes
+	### (foo, bar and baz), and no changes will be preserved. Whether
+	### the changes were staged pre- or post-merge does not matter
+	### (except for not preventing starting the merge).
+	### Change expectations accordingly:
+	rm expect expect-staged &&
+	touch expect &&
+	touch expect-staged &&
+	# Abort merge
+	git merge --abort &&
+	test ! -f .git/MERGE_HEAD &&
+	test "$pre_merge_head" = "$(git rev-parse HEAD)" &&
+	git diff > actual &&
+	test_cmp expect actual &&
+	git diff --staged > actual-staged &&
+	test_cmp expect-staged actual-staged
+'
+
+test_done
-- 
1.7.3.2.173.gab1c9.dirty