[PATCH 1/2] worktree: fix worktree add race.

[Michal Suchanek <msuchanek@suse.de>]

Git runs a stat loop to find a worktree name that's available and then does
mkdir on the found name. Turn it to mkdir loop to avoid another invocation of
worktree add finding the same free name and creating the directory first.

Signed-off-by: Michal Suchanek <msuchanek@suse.de>
---
 builtin/worktree.c | 11 ++++++-----
 1 file changed, 6 insertions(+), 5 deletions(-)

diff --git a/builtin/worktree.c b/builtin/worktree.c
index 3f9907fcc994..e1a2a56c03c5 100644
--- a/builtin/worktree.c
+++ b/builtin/worktree.c
@@ -268,10 +268,9 @@ static int add_worktree(const char *path, const char *refname,
 	struct strbuf sb_git = STRBUF_INIT, sb_repo = STRBUF_INIT;
 	struct strbuf sb = STRBUF_INIT;
 	const char *name;
-	struct stat st;
 	struct child_process cp = CHILD_PROCESS_INIT;
 	struct argv_array child_env = ARGV_ARRAY_INIT;
-	int counter = 0, len, ret;
+	int counter = 1, len, ret;
 	struct strbuf symref = STRBUF_INIT;
 	struct commit *commit = NULL;
 	int is_branch = 0;
@@ -295,19 +294,21 @@ static int add_worktree(const char *path, const char *refname,
 	if (safe_create_leading_directories_const(sb_repo.buf))
 		die_errno(_("could not create leading directories of '%s'"),
 			  sb_repo.buf);
-	while (!stat(sb_repo.buf, &st)) {
+
+	while (mkdir(sb_repo.buf, 0777)) {
 		counter++;
+		if(!counter) break; /* don't loop forever */
 		strbuf_setlen(&sb_repo, len);
 		strbuf_addf(&sb_repo, "%d", counter);
 	}
+	if (!counter)
+		die_errno(_("could not create directory of '%s'"), sb_repo.buf);
 	name = strrchr(sb_repo.buf, '/') + 1;
 
 	junk_pid = getpid();
 	atexit(remove_junk);
 	sigchain_push_common(remove_junk_on_signal);
 
-	if (mkdir(sb_repo.buf, 0777))
-		die_errno(_("could not create directory of '%s'"), sb_repo.buf);
 	junk_git_dir = xstrdup(sb_repo.buf);
 	is_junk = 1;
 
-- 
2.20.1