[PATCH] notes: handle multiple worktrees

[David Turner <dturner@twopensource.com>]

Prevent merges to the same notes branch from different worktrees.
Before creating NOTES_MERGE_REF, check NOTES_MERGE_REF using the same
code we use to check that two HEADs in different worktrees don't point
to the same branch.  Modify that code, die_if_checked_out, to take a
"head" ref to examine; previously, it just looked at HEAD.

Reported-by: Junio C Hamano <gitster@pobox.com>
Signed-off-by: David Turner <dturner@twopensource.com>
---
 branch.c                         | 15 +++++----
 branch.h                         |  2 +-
 builtin/checkout.c               |  2 +-
 builtin/notes.c                  |  2 ++
 builtin/worktree.c               |  2 +-
 t/t3320-notes-merge-worktrees.sh | 71 ++++++++++++++++++++++++++++++++++++++++
 6 files changed, 84 insertions(+), 10 deletions(-)
 create mode 100755 t/t3320-notes-merge-worktrees.sh

diff --git a/branch.c b/branch.c
index c85be07..60eadc6 100644
--- a/branch.c
+++ b/branch.c
@@ -311,21 +311,22 @@ void remove_branch_state(void)
 	unlink(git_path("SQUASH_MSG"));
 }
 
-static void check_linked_checkout(const char *branch, const char *id)
+static void check_linked_checkout(const char *head, const char *branch,
+				  const char *id)
 {
 	struct strbuf sb = STRBUF_INIT;
 	struct strbuf path = STRBUF_INIT;
 	struct strbuf gitdir = STRBUF_INIT;
 
 	/*
-	 * $GIT_COMMON_DIR/HEAD is practically outside
+	 * $GIT_COMMON_DIR/$head is practically outside
 	 * $GIT_DIR so resolve_ref_unsafe() won't work (it
 	 * uses git_path). Parse the ref ourselves.
 	 */
 	if (id)
-		strbuf_addf(&path, "%s/worktrees/%s/HEAD", get_git_common_dir(), id);
+		strbuf_addf(&path, "%s/worktrees/%s/%s", get_git_common_dir(), id, head);
 	else
-		strbuf_addf(&path, "%s/HEAD", get_git_common_dir());
+		strbuf_addf(&path, "%s/%s", get_git_common_dir(), head);
 
 	if (!strbuf_readlink(&sb, path.buf, 0)) {
 		if (!starts_with(sb.buf, "refs/") ||
@@ -356,13 +357,13 @@ done:
 	strbuf_release(&gitdir);
 }
 
-void die_if_checked_out(const char *branch)
+void die_if_checked_out(const char *head, const char *branch)
 {
 	struct strbuf path = STRBUF_INIT;
 	DIR *dir;
 	struct dirent *d;
 
-	check_linked_checkout(branch, NULL);
+	check_linked_checkout(head, branch, NULL);
 
 	strbuf_addf(&path, "%s/worktrees", get_git_common_dir());
 	dir = opendir(path.buf);
@@ -373,7 +374,7 @@ void die_if_checked_out(const char *branch)
 	while ((d = readdir(dir)) != NULL) {
 		if (!strcmp(d->d_name, ".") || !strcmp(d->d_name, ".."))
 			continue;
-		check_linked_checkout(branch, d->d_name);
+		check_linked_checkout(head, branch, d->d_name);
 	}
 	closedir(dir);
 }
diff --git a/branch.h b/branch.h
index 58aa45f..3577fe5 100644
--- a/branch.h
+++ b/branch.h
@@ -57,6 +57,6 @@ extern int read_branch_desc(struct strbuf *, const char *branch_name);
  * worktree and die (with a message describing its checkout location) if
  * it is.
  */
-extern void die_if_checked_out(const char *branch);
+extern void die_if_checked_out(const char *head, const char *branch);
 
 #endif
diff --git a/builtin/checkout.c b/builtin/checkout.c
index e1403be..a5e9f2d 100644
--- a/builtin/checkout.c
+++ b/builtin/checkout.c
@@ -1107,7 +1107,7 @@ static int checkout_branch(struct checkout_opts *opts,
 		char *head_ref = resolve_refdup("HEAD", 0, sha1, &flag);
 		if (head_ref &&
 		    (!(flag & REF_ISSYMREF) || strcmp(head_ref, new->path)))
-			die_if_checked_out(new->path);
+			die_if_checked_out("HEAD", new->path);
 		free(head_ref);
 	}
 
diff --git a/builtin/notes.c b/builtin/notes.c
index 63f95fc..8794ba1 100644
--- a/builtin/notes.c
+++ b/builtin/notes.c
@@ -19,6 +19,7 @@
 #include "string-list.h"
 #include "notes-merge.h"
 #include "notes-utils.h"
+#include "branch.h"
 
 static const char * const git_notes_usage[] = {
 	N_("git notes [--ref <notes-ref>] [list [<object>]]"),
@@ -829,6 +830,7 @@ static int merge(int argc, const char **argv, const char *prefix)
 		update_ref(msg.buf, "NOTES_MERGE_PARTIAL", result_sha1, NULL,
 			   0, UPDATE_REFS_DIE_ON_ERR);
 		/* Store ref-to-be-updated into .git/NOTES_MERGE_REF */
+		die_if_checked_out("NOTES_MERGE_REF", default_notes_ref());
 		if (create_symref("NOTES_MERGE_REF", default_notes_ref(), NULL))
 			die("Failed to store link to current notes ref (%s)",
 			    default_notes_ref());
diff --git a/builtin/worktree.c b/builtin/worktree.c
index 430b51e..bfdb90f 100644
--- a/builtin/worktree.c
+++ b/builtin/worktree.c
@@ -203,7 +203,7 @@ static int add_worktree(const char *path, const char *refname,
 	else if (!opts->detach && !strbuf_check_branch_ref(&symref, refname) &&
 		 ref_exists(symref.buf)) { /* it's a branch */
 		if (!opts->force)
-			die_if_checked_out(symref.buf);
+			die_if_checked_out("HEAD", symref.buf);
 	} else { /* must be a commit */
 		commit = lookup_commit_reference_by_name(refname);
 		if (!commit)
diff --git a/t/t3320-notes-merge-worktrees.sh b/t/t3320-notes-merge-worktrees.sh
new file mode 100755
index 0000000..b102c23
--- /dev/null
+++ b/t/t3320-notes-merge-worktrees.sh
@@ -0,0 +1,71 @@
+#!/bin/sh
+#
+# Copyright (c) 2015 Twitter, Inc
+#
+
+test_description='Test merging of notes trees in multiple worktrees'
+
+. ./test-lib.sh
+
+test_expect_success 'setup commit' '
+	test_commit tantrum
+'
+
+commit_tantrum=$(git rev-parse tantrum^{commit})
+
+test_expect_success 'setup notes ref (x)' '
+	git config core.notesRef refs/notes/x &&
+	git notes add -m "x notes on tantrum" tantrum
+'
+
+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 remove tantrum
+'
+
+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 "conflicting notes on tantrum" tantrum
+'
+
+test_expect_success 'modify notes ref ourselves (x)' '
+	git config core.notesRef refs/notes/x &&
+	git notes add -f -m "more conflicting notes on tantrum" tantrum
+'
+
+test_expect_success 'create some new worktrees' '
+	git worktree add -b newbranch worktree master &&
+	git worktree add -b newbranch2 worktree2 master
+'
+
+test_expect_success 'merge z into y fails and sets NOTES_MERGE_REF' '
+	git config core.notesRef refs/notes/y &&
+	test_must_fail git notes merge z &&
+	echo "ref: refs/notes/y" > expect &&
+	test_cmp .git/NOTES_MERGE_REF expect
+'
+
+test_expect_success 'merge z into y while mid-merge in another workdir fails' '
+	(
+		cd worktree &&
+		git config core.notesRef refs/notes/y &&
+		test_must_fail git notes merge z 2>err &&
+		grep "is already checked out" err
+	) &&
+	test_path_is_missing .git/worktrees/worktree/NOTES_MERGE_REF
+'
+
+test_expect_success 'merge z into x while mid-merge on y succeeds' '
+	(
+		cd worktree2 &&
+		git config core.notesRef refs/notes/x &&
+		test_must_fail git notes merge z 2>&1 >out &&
+		grep -v "is already checked out" out
+	) &&
+	echo "ref: refs/notes/x" > expect &&
+	test_cmp .git/worktrees/worktree2/NOTES_MERGE_REF expect
+'
+
+test_done
-- 
2.0.4.315.gad8727a-twtrsrc