builtin-bundle create - use lock_file

"git bundle create" left an invalid, partially written bundle if
an error occured during creation.

Signed-off-by: Junio C Hamano <gitster@pobox.com>

builtin-bundle.c

@@ -189,7 +189,9 @@ static int list_heads(struct bundle_header *header, int argc, const char **argv)
 static int create_bundle(struct bundle_header *header, const char *path,
 		int argc, const char **argv)
 {
+	static struct lock_file lock;
 	int bundle_fd = -1;
+	int bundle_to_stdout;
 	const char **argv_boundary = xmalloc((argc + 4) * sizeof(const char *));
 	const char **argv_pack = xmalloc(5 * sizeof(const char *));
 	int i, ref_count = 0;
@@ -198,14 +200,11 @@ static int create_bundle(struct bundle_header *header, const char *path,
 	struct child_process rls;
 	FILE *rls_fout;
 
-	/*
-	 * NEEDSWORK: this should use something like lock-file
-	 * to create temporary that is cleaned up upon error.
-	 */
-	bundle_fd = (!strcmp(path, "-") ? 1 :
-			open(path, O_CREAT | O_EXCL | O_WRONLY, 0666));
-	if (bundle_fd < 0)
-		return error("Could not create '%s': %s", path, strerror(errno));
+	bundle_to_stdout = !strcmp(path, "-");
+	if (bundle_to_stdout)
+		bundle_fd = 1;
+	else
+		bundle_fd = hold_lock_file_for_update(&lock, path, 1);
 
 	/* write signature */
 	write_or_die(bundle_fd, bundle_signature, strlen(bundle_signature));
@@ -341,6 +340,9 @@ static int create_bundle(struct bundle_header *header, const char *path,
 	}
 	if (finish_command(&rls))
 		return error ("pack-objects died");
+	close(bundle_fd);
+	if (!bundle_to_stdout)
+		commit_lock_file(&lock);
 	return 0;
 }