have index-pack create .keep file more carefully

If by chance we receive a pack which content (list of objects) matches
another pack that we already have, and if that pack is marked with a
.keep file, then we should not overwrite it.

Signed-off-by: Nicolas Pitre <nico@cam.org>
Signed-off-by: Junio C Hamano <junkio@cox.net>

diff --git a/index-pack.c b/index-pack.c
index a3b55f9b0f07d39d3f2d7be184d250289abdb3da..8d64a883afe0b9868ae6c8d918986785ee3cdcfe 100644 (file)
--- a/index-pack.c
+++ b/index-pack.c
@@ -788,14 +788,17 @@ static void final(const char *final_pack_name, const char *curr_pack_name,
                                 get_object_directory(), sha1_to_hex(sha1));
                        keep_name = name;
                }
-               keep_fd = open(keep_name, O_RDWR | O_CREAT, 0600);
-               if (keep_fd < 0)
-                       die("cannot write keep file");
-               if (keep_msg_len > 0) {
-                       write_or_die(keep_fd, keep_msg, keep_msg_len);
-                       write_or_die(keep_fd, "\n", 1);
+               keep_fd = open(keep_name, O_RDWR|O_CREAT|O_EXCL, 0600);
+               if (keep_fd < 0) {
+                       if (errno != EEXIST)
+                               die("cannot write keep file");
+               } else {
+                       if (keep_msg_len > 0) {
+                               write_or_die(keep_fd, keep_msg, keep_msg_len);
+                               write_or_die(keep_fd, "\n", 1);
+                       }
+                       close(keep_fd);
                }
-               close(keep_fd);
        }
 
        if (final_pack_name != curr_pack_name) {