[PATCH 11/20] worktree.c: recognize no main worktree

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

Because HEAD is part of repository signature, even if it's per-worktree
file, we can't simply delete it. So main worktree is considered gone if
.git/HEAD contains all-zero SHA-1.

Signed-off-by: Nguyễn Thái Ngọc Duy <pclouds@gmail.com>
---
 worktree.c | 2 ++
 1 file changed, 2 insertions(+)

diff --git a/worktree.c b/worktree.c
index e878f49..80c525b 100644
--- a/worktree.c
+++ b/worktree.c
@@ -49,6 +49,8 @@ static int parse_ref(char *path_to_ref, struct strbuf *ref, int *is_detached)
 		if (!starts_with(ref->buf, "ref:")) {
 			if (is_detached)
 				*is_detached = 1;
+			if (starts_with(ref->buf, sha1_to_hex(null_sha1)))
+				return -1;
 		} else {
 			strbuf_remove(ref, 0, strlen("ref:"));
 			strbuf_trim(ref);
-- 
2.7.0.377.g4cd97dd