notes-merge: Don't remove .git/NOTES_MERGE_WORKTREE; it may be the user's cwd

When a manual notes merge is committed or aborted, we need to remove the
temporary worktree at .git/NOTES_MERGE_WORKTREE. However, removing the
entire directory is not good if the user ran the 'git notes merge
--commit/--abort' from within that directory. On Windows, the directory
removal would simply fail, while on POSIX systems, users would suddenly
find themselves in an invalid current directory.

Therefore, instead of deleting the entire directory, we delete everything
_within_ the directory, and leave the (empty) directory in place.

This would cause a subsequent notes merge to abort, complaining about a
previous - unfinished - notes merge (due to the presence of
.git/NOTES_MERGE_WORKTREE), so we also need to adjust this check to only
trigger when .git/NOTES_MERGE_WORKTREE is non-empty.

Finally, adjust the t3310 manual notes merge testcases to correctly handle
the existence of an empty .git/NOTES_MERGE_WORKTREE directory.

Inspired-by: Junio C Hamano <[email protected]>
Signed-off-by: Johan Herland <[email protected]>
Signed-off-by: Junio C Hamano <[email protected]>

Author: jherland

notes-merge.c

@@ -267,7 +267,8 @@ static void check_notes_merge_worktree(struct notes_merge_options *o)
 		 * Must establish NOTES_MERGE_WORKTREE.
 		 * Abort if NOTES_MERGE_WORKTREE already exists
 		 */
-		if (file_exists(git_path(NOTES_MERGE_WORKTREE))) {
+		if (file_exists(git_path(NOTES_MERGE_WORKTREE)) &&
+		    !is_empty_dir(git_path(NOTES_MERGE_WORKTREE))) {
 			if (advice_resolve_conflict)
 				die("You have not concluded your previous "
 				    "notes merge (%s exists).\nPlease, use "
@@ -756,14 +757,18 @@ int notes_merge_commit(struct notes_merge_options *o,
 
 int notes_merge_abort(struct notes_merge_options *o)
 {
-	/* Remove .git/NOTES_MERGE_WORKTREE directory and all files within */
+	/*
+	 * Remove all files within .git/NOTES_MERGE_WORKTREE. We do not remove
+	 * the .git/NOTES_MERGE_WORKTREE directory itself, since it might be
+	 * the current working directory of the user.
+	 */
 	struct strbuf buf = STRBUF_INIT;
 	int ret;
 
 	strbuf_addstr(&buf, git_path(NOTES_MERGE_WORKTREE));
 	if (o->verbosity >= 3)
-		printf("Removing notes merge worktree at %s\n", buf.buf);
-	ret = remove_dir_recursively(&buf, 0);
+		printf("Removing notes merge worktree at %s/*\n", buf.buf);
+	ret = remove_dir_recursively(&buf, REMOVE_DIR_KEEP_TOPLEVEL);
 	strbuf_release(&buf);
 	return ret;
 }

t/t3310-notes-merge-manual-resolve.sh

@@ -324,7 +324,7 @@ 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_might_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)" &&
@@ -386,7 +386,7 @@ test_expect_success 'redo merge of z into m (== y) with default ("manual") resol
 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_might_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)" &&
@@ -453,7 +453,7 @@ EOF
 	# Finalize merge
 	git notes merge --commit &&
 	# No .git/NOTES_MERGE_* files left
-	test_must_fail ls .git/NOTES_MERGE_* >output 2>/dev/null &&
+	test_might_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)" &&
@@ -542,7 +542,7 @@ EOF
 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_might_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)" &&