[PATCH] worktree add: be tolerant of corrupt worktrees

["Nguyễn Thái Ngọc Duy" <pclouds@gmail.com>]

find_worktree() can die() unexpectedly because it uses real_path()
instead of the gentler version. When it's used in 'git worktree add' [1]
and there's a bad worktree, this die() could prevent people from adding
new worktrees.

The "bad" condition to trigger this is when a parent of the worktree's
location is deleted. Then real_path() will complain.

Use the other version so that bad worktrees won't affect 'worktree
add'. The bad ones will eventually be pruned, we just have to tolerate
them for a bit.

[1] added in cb56f55c16 (worktree: disallow adding same path multiple
    times, 2018-08-28), or since v2.20.0. Though the real bug in
    find_worktree() is much older.

Reported-by: Shaheed Haque <shaheedhaque@gmail.com>
Signed-off-by: Nguyễn Thái Ngọc Duy <pclouds@gmail.com>
---
 t/t2025-worktree-add.sh | 12 ++++++++++++
 worktree.c              |  7 +++++--
 2 files changed, 17 insertions(+), 2 deletions(-)

diff --git a/t/t2025-worktree-add.sh b/t/t2025-worktree-add.sh
index 286bba35d8..d83a9f0fdc 100755
--- a/t/t2025-worktree-add.sh
+++ b/t/t2025-worktree-add.sh
@@ -570,4 +570,16 @@ test_expect_success '"add" an existing locked but missing worktree' '
 	git worktree add --force --force --detach gnoo
 '
 
+test_expect_success '"add" should not fail because of another bad worktree' '
+	git init add-fail &&
+	(
+		cd add-fail &&
+		test_commit first &&
+		mkdir sub &&
+		git worktree add sub/to-be-deleted &&
+		rm -rf sub &&
+		git worktree add second
+	)
+'
+
 test_done
diff --git a/worktree.c b/worktree.c
index d6a0ee7f73..c79b3e42bb 100644
--- a/worktree.c
+++ b/worktree.c
@@ -222,9 +222,12 @@ struct worktree *find_worktree(struct worktree **list,
 		free(to_free);
 		return NULL;
 	}
-	for (; *list; list++)
-		if (!fspathcmp(path, real_path((*list)->path)))
+	for (; *list; list++) {
+		const char *wt_path = real_path_if_valid((*list)->path);
+
+		if (wt_path && !fspathcmp(path, wt_path))
 			break;
+	}
 	free(path);
 	free(to_free);
 	return *list;
-- 
2.21.0.1141.gd54ac2cb17