clean: show an error message when the path is too long

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

In particular on Windows, where the default maximum path length is quite
small (yet there are ways to circumvent that limit in many cases), it is
very important that users be given an indication why their command
failed because of too long paths when it did.

This test case makes sure that a warning is issued that would have
helped the user who reported this issue:

	git-for-windows#521

Signed-off-by: Johannes Schindelin <[email protected]>

Author: dscho

builtin/clean.c

@@ -194,7 +194,8 @@ 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;

t/t7300-clean.sh

@@ -669,4 +669,15 @@ test_expect_success 'git clean -d skips untracked dirs containing ignored files'
 	test_path_is_missing foo/b/bb
 '
 
+test_expect_success MINGW 'handle clean & core.longpaths = false nicely' '
+	git config core.longpaths false &&
+	test_when_finished git config --unset core.longpaths &&
+	a50=aaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaa &&
+	mkdir -p $a50$a50/$a50$a50/$a50$a50 &&
+	touch $a50$a50/test.txt &&
+	touch $a50$a50/$a50$a50/$a50$a50/test.txt &&
+	test_must_fail git clean -xdf 2>.git/err &&
+	grep "too long" .git/err
+'
+
 test_done