[PATCH v4 0/4] Add --graft option to git replace

[PATCH v4 0/4] Add --graft option to git replace

[Christian Couder]

Here is a small patch series to implement:

        git replace [-f] --graft <commit> [<parent>...]

This patch series goes on top of the patch series that
implements --edit.

The changes since v3, thanks to Junio, are:

- remove function read_sha1_commit() and its call as well as a
  call to parse_commit_buffer(), as lookup_commit_or_die()
  already reads the commit buffer and parses it (patch 1/4)

- source git-sh-setup and other small cosmetic changes in
  convert-grafts-to-replace-refs.sh (patch 4/4)

Christian Couder (4):
  replace: add --graft option
  replace: add test for --graft
  Documentation: replace: add --graft option
  contrib: add convert-grafts-to-replace-refs.sh

 Documentation/git-replace.txt             | 10 +++++
 builtin/replace.c                         | 62 ++++++++++++++++++++++++++++++-
 contrib/convert-grafts-to-replace-refs.sh | 28 ++++++++++++++
 t/t6050-replace.sh                        | 12 ++++++
 4 files changed, 111 insertions(+), 1 deletion(-)
 create mode 100755 contrib/convert-grafts-to-replace-refs.sh

-- 
2.0.0.rc0.40.gd30ccc4

[PATCH v4 1/4] replace: add --graft option

[Christian Couder]

The usage string for this option is:

git replace [-f] --graft <commit> [<parent>...]

First we create a new commit that is the same as <commit>
except that its parents are [<parents>...]

Then we create a replace ref that replace <commit> with
the commit we just created.

With this new option, it should be straightforward to
convert grafts to replace refs.

Signed-off-by: Christian Couder <chriscool@tuxfamily.org>
---
 builtin/replace.c | 62 ++++++++++++++++++++++++++++++++++++++++++++++++++++++-
 1 file changed, 61 insertions(+), 1 deletion(-)

diff --git a/builtin/replace.c b/builtin/replace.c
index 1bb491d..91eda61 100644
--- a/builtin/replace.c
+++ b/builtin/replace.c
@@ -17,6 +17,7 @@
 static const char * const git_replace_usage[] = {
 	N_("git replace [-f] <object> <replacement>"),
 	N_("git replace [-f] --edit <object>"),
+	N_("git replace [-f] --graft <commit> [<parent>...]"),
 	N_("git replace -d <object>..."),
 	N_("git replace [--format=<format>] [-l [<pattern>]]"),
 	NULL
@@ -294,6 +295,54 @@ static int edit_and_replace(const char *object_ref, int force)
 	return replace_object_sha1(object_ref, old, "replacement", new, force);
 }
 
+static int create_graft(int argc, const char **argv, int force)
+{
+	unsigned char old[20], new[20];
+	const char *old_ref = argv[0];
+	struct commit *commit;
+	struct strbuf buf = STRBUF_INIT;
+	struct strbuf new_parents = STRBUF_INIT;
+	const char *parent_start, *parent_end;
+	int i;
+
+	if (get_sha1(old_ref, old) < 0)
+		die(_("Not a valid object name: '%s'"), old_ref);
+	commit = lookup_commit_or_die(old, old_ref);
+
+	/* find existing parents */
+	strbuf_addstr(&buf, commit->buffer);
+	parent_start = buf.buf;
+	parent_start += 46; /* "tree " + "hex sha1" + "\n" */
+	parent_end = parent_start;
+
+	while (starts_with(parent_end, "parent "))
+		parent_end += 48; /* "parent " + "hex sha1" + "\n" */
+
+	/* prepare new parents */
+	for (i = 1; i < argc; i++) {
+		unsigned char sha1[20];
+		if (get_sha1(argv[i], sha1) < 0)
+			die(_("Not a valid object name: '%s'"), argv[i]);
+		lookup_commit_or_die(sha1, argv[i]);
+		strbuf_addf(&new_parents, "parent %s\n", sha1_to_hex(sha1));
+	}
+
+	/* replace existing parents with new ones */
+	strbuf_splice(&buf, parent_start - buf.buf, parent_end - parent_start,
+		      new_parents.buf, new_parents.len);
+
+	if (write_sha1_file(buf.buf, buf.len, commit_type, new))
+		die(_("could not write replacement commit for: '%s'"), old_ref);
+
+	strbuf_release(&new_parents);
+	strbuf_release(&buf);
+
+	if (!hashcmp(old, new))
+		return error("new commit is the same as the old one: '%s'", sha1_to_hex(old));
+
+	return replace_object_sha1(old_ref, old, "replacement", new, force);
+}
+
 int cmd_replace(int argc, const char **argv, const char *prefix)
 {
 	int force = 0;
@@ -303,12 +352,14 @@ int cmd_replace(int argc, const char **argv, const char *prefix)
 		MODE_LIST,
 		MODE_DELETE,
 		MODE_EDIT,
+		MODE_GRAFT,
 		MODE_REPLACE
 	} cmdmode = MODE_UNSPECIFIED;
 	struct option options[] = {
 		OPT_CMDMODE('l', "list", &cmdmode, N_("list replace refs"), MODE_LIST),
 		OPT_CMDMODE('d', "delete", &cmdmode, N_("delete replace refs"), MODE_DELETE),
 		OPT_CMDMODE('e', "edit", &cmdmode, N_("edit existing object"), MODE_EDIT),
+		OPT_CMDMODE('g', "graft", &cmdmode, N_("change a commit's parents"), MODE_GRAFT),
 		OPT_BOOL('f', "force", &force, N_("replace the ref if it exists")),
 		OPT_STRING(0, "format", &format, N_("format"), N_("use this format")),
 		OPT_END()
@@ -325,7 +376,10 @@ int cmd_replace(int argc, const char **argv, const char *prefix)
 		usage_msg_opt("--format cannot be used when not listing",
 			      git_replace_usage, options);
 
-	if (force && cmdmode != MODE_REPLACE && cmdmode != MODE_EDIT)
+	if (force &&
+	    cmdmode != MODE_REPLACE &&
+	    cmdmode != MODE_EDIT &&
+	    cmdmode != MODE_GRAFT)
 		usage_msg_opt("-f only makes sense when writing a replacement",
 			      git_replace_usage, options);
 
@@ -348,6 +402,12 @@ int cmd_replace(int argc, const char **argv, const char *prefix)
 				      git_replace_usage, options);
 		return edit_and_replace(argv[0], force);
 
+	case MODE_GRAFT:
+		if (argc < 1)
+			usage_msg_opt("-g needs at least one argument",
+				      git_replace_usage, options);
+		return create_graft(argc, argv, force);
+
 	case MODE_LIST:
 		if (argc > 1)
 			usage_msg_opt("only one pattern can be given with -l",
-- 
2.0.0.rc0.40.gd30ccc4

[PATCH v4 2/4] replace: add test for --graft

[Christian Couder]

Signed-off-by: Christian Couder <chriscool@tuxfamily.org>
---
 t/t6050-replace.sh | 12 ++++++++++++
 1 file changed, 12 insertions(+)

diff --git a/t/t6050-replace.sh b/t/t6050-replace.sh
index 68b3cb2..ca45a84 100755
--- a/t/t6050-replace.sh
+++ b/t/t6050-replace.sh
@@ -351,4 +351,16 @@ test_expect_success 'replace ref cleanup' '
 	test -z "$(git replace)"
 '
 
+test_expect_success '--graft with and without already replaced object' '
+	test $(git log --oneline | wc -l) = 7 &&
+	git replace --graft $HASH5 &&
+	test $(git log --oneline | wc -l) = 3 &&
+	git cat-file -p $HASH5 | test_must_fail grep parent &&
+	test_must_fail git replace --graft $HASH5 $HASH4 $HASH3 &&
+	git replace --force -g $HASH5 $HASH4 $HASH3 &&
+	git cat-file -p $HASH5 | grep "parent $HASH4" &&
+	git cat-file -p $HASH5 | grep "parent $HASH3" &&
+	git replace -d $HASH5
+'
+
 test_done
-- 
2.0.0.rc0.40.gd30ccc4

[PATCH v4 3/4] Documentation: replace: add --graft option

[Christian Couder]

Signed-off-by: Christian Couder <chriscool@tuxfamily.org>
---
 Documentation/git-replace.txt | 8 ++++++++
 1 file changed, 8 insertions(+)

diff --git a/Documentation/git-replace.txt b/Documentation/git-replace.txt
index 61461b9..491875e 100644
--- a/Documentation/git-replace.txt
+++ b/Documentation/git-replace.txt
@@ -10,6 +10,7 @@ SYNOPSIS
 [verse]
 'git replace' [-f] <object> <replacement>
 'git replace' [-f] --edit <object>
+'git replace' [-f] --graft <commit> [<parent>...]
 'git replace' -d <object>...
 'git replace' [--format=<format>] [-l [<pattern>]]
 
@@ -73,6 +74,13 @@ OPTIONS
 	newly created object. See linkgit:git-var[1] for details about
 	how the editor will be chosen.
 
+--graft <commit> [<parent>...]::
+	Create a graft commit. A new commit is created with the same
+	content as <commit> except that its parents will be
+	[<parent>...] instead of <commit>'s parents. A replacement ref
+	is then created to replace <commit> with the newly created
+	commit.
+
 -l <pattern>::
 --list <pattern>::
 	List replace refs for objects that match the given pattern (or
-- 
2.0.0.rc0.40.gd30ccc4

[PATCH v4 4/4] contrib: add convert-grafts-to-replace-refs.sh

[Christian Couder]

This patch adds into contrib/ an example script to convert
grafts from an existing grafts file into replace refs using
the new --graft option of "git replace".

While at it let's mention this new script in the
"git replace" documentation for the --graft option.

Signed-off-by: Christian Couder <chriscool@tuxfamily.org>
---
 Documentation/git-replace.txt             |  4 +++-
 contrib/convert-grafts-to-replace-refs.sh | 28 ++++++++++++++++++++++++++++
 2 files changed, 31 insertions(+), 1 deletion(-)
 create mode 100755 contrib/convert-grafts-to-replace-refs.sh

diff --git a/Documentation/git-replace.txt b/Documentation/git-replace.txt
index 491875e..e1be2e6 100644
--- a/Documentation/git-replace.txt
+++ b/Documentation/git-replace.txt
@@ -79,7 +79,9 @@ OPTIONS
 	content as <commit> except that its parents will be
 	[<parent>...] instead of <commit>'s parents. A replacement ref
 	is then created to replace <commit> with the newly created
-	commit.
+	commit. See contrib/convert-grafts-to-replace-refs.sh for an
+	example script based on this option that can convert grafts to
+	replace refs.
 
 -l <pattern>::
 --list <pattern>::
diff --git a/contrib/convert-grafts-to-replace-refs.sh b/contrib/convert-grafts-to-replace-refs.sh
new file mode 100755
index 0000000..0cbc917
--- /dev/null
+++ b/contrib/convert-grafts-to-replace-refs.sh
@@ -0,0 +1,28 @@
+#!/bin/sh
+
+# You should execute this script in the repository where you
+# want to convert grafts to replace refs.
+
+GRAFTS_FILE="${GIT_DIR:-.git}/info/grafts"
+
+. $(git --exec-path)/git-sh-setup
+
+test -f "$GRAFTS_FILE" || die "Could not find graft file: '$GRAFTS_FILE'"
+
+grep '^[^# ]' "$GRAFTS_FILE" |
+while read definition
+do
+	if test -n "$definition"
+	then
+		echo "Converting: $definition"
+		git replace --graft $definition ||
+			die "Conversion failed for: $definition"
+	fi
+done
+
+mv "$GRAFTS_FILE" "$GRAFTS_FILE.bak" ||
+	die "Could not rename '$GRAFTS_FILE' to '$GRAFTS_FILE.bak'"
+
+echo "Success!"
+echo "All the grafts in '$GRAFTS_FILE' have been converted to replace refs!"
+echo "The grafts file '$GRAFTS_FILE' has been renamed: '$GRAFTS_FILE.bak'"
-- 
2.0.0.rc0.40.gd30ccc4