remove_dirs: do not swallow error when stat() failed

Without an error message when stat() failed, e.g. `git clean` would
abort without an error message, leaving the user quite puzzled.

This fixes #521

Signed-off-by: Johannes Schindelin <johannes.schindelin@gmx.de>

builtin/clean.c

@@ -192,7 +192,8 @@ static int remove_dirs(struct strbuf *path, const char *prefix, int force_flag,
 		strbuf_setlen(path, len);
 		strbuf_addstr(path, e->d_name);
 		if (lstat(path->buf, &st))
-			; /* fall thru */
+			warning("Could not stat path '%s': %s",
+				path->buf, strerror(errno));
 		else if (S_ISDIR(st.st_mode)) {
 			if (remove_dirs(path, prefix, force_flag, dry_run, quiet, &gone))
 				ret = 1;