Prevent git-upload-pack segfault if object cannot be found

Signed-off-by: Carl Worth <cworth@cworth.org>
Signed-off-by: Junio C Hamano <junkio@cox.net>

sha1_file.c

@@ -551,8 +551,10 @@ static void prepare_packed_git_one(char *objdir, int local)
 	sprintf(path, "%s/pack", objdir);
 	len = strlen(path);
 	dir = opendir(path);
-	if (!dir)
+	if (!dir) {
+		fprintf(stderr, "unable to open object pack directory: %s: %s\n", path, strerror(errno));
 		return;
+	}
 	path[len++] = '/';
 	while ((de = readdir(dir)) != NULL) {
 		int namelen = strlen(de->d_name);

upload-pack.c

@@ -216,6 +216,9 @@ static int send_ref(const char *refname, const unsigned char *sha1)
 	static char *capabilities = "multi_ack";
 	struct object *o = parse_object(sha1);
 
+	if (!o)
+		die("git-upload-pack: cannot find object %s:", sha1_to_hex(sha1));
+
 	if (capabilities)
 		packet_write(1, "%s %s%c%s\n", sha1_to_hex(sha1), refname,
 			0, capabilities);