[PATCH v2] notes: handle multiple worktrees

[David Turner <dturner@twopensource.com>]

Before creating NOTES_MERGE_REF, check NOTES_MERGE_REF using
die_if_shared_symref.  This prevents simultaneous merges to the same
notes branch from different worktrees.

Signed-off-by: David Turner <dturner@twopensource.com>
---

This version addresses Eric Sunshine's critiques of v1.  It breaks out
the symref-checking functionality into die_if_shared_symref, leaving
die_if_checked_out to handle HEAD.

---
 builtin/notes.c                  |  2 ++
 t/t3320-notes-merge-worktrees.sh | 71 ++++++++++++++++++++++++++++++++++++++++
 2 files changed, 73 insertions(+)
 create mode 100755 t/t3320-notes-merge-worktrees.sh

diff --git a/builtin/notes.c b/builtin/notes.c
index 63f95fc..78a264e 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_shared_symref("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/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