builtin/commit: remove unnecessary variable definition

The file descriptor is already defined at the beginning of the function.
Signed-off-by: NMarkus Heidelberg <markus.heidelberg@web.de>
Signed-off-by: NJunio C Hamano <gitster@pobox.com>

builtin/commit.c

@@ -307,7 +307,7 @@ static char *prepare_index(int argc, const char **argv, const char *prefix, int
 	 * (B) on failure, rollback the real index.
 	 */
 	if (all || (also && pathspec && *pathspec)) {
-		int fd = hold_locked_index(&index_lock, 1);
+		fd = hold_locked_index(&index_lock, 1);
 		add_files_to_cache(also ? prefix : NULL, pathspec, 0);
 		refresh_cache_or_die(refresh_flags);
 		if (write_cache(fd, active_cache, active_nr) ||