[PATCH v2 2/2] clean: avoid traversing into untracked dirs when unnecessary

[Patrick Marlier <patrick.marlier@gmail.com>]

When deleting all untracked and ignored files and any nested
repositories (such as with `git clean -ffdx`), we do not need to recurse
into an untracked directory to see if any of the entries under it are
ignored or a nested repository.  Special case this condition to avoid
unnecessary recursion.
---
 builtin/clean.c  |  4 +++-
 t/t7300-clean.sh | 24 ++++++++++++++++++++++++
 2 files changed, 27 insertions(+), 1 deletion(-)

diff --git a/builtin/clean.c b/builtin/clean.c
index 18b37e3fd9..1b1454d052 100644
--- a/builtin/clean.c
+++ b/builtin/clean.c
@@ -978,7 +978,9 @@ int cmd_clean(int argc, const char **argv, const char *prefix)
 		remove_directories = 1;
 	}
 
-	if (remove_directories && !ignored_only) {
+	if (remove_directories && ignored && !exclude_list.nr && force > 1)
+		; /* No need to recurse to look for ignored files */
+	else if (remove_directories && !ignored_only) {
 		/*
 		 * We need to know about ignored files too:
 		 *
diff --git a/t/t7300-clean.sh b/t/t7300-clean.sh
index 0399701e62..ceab7c4883 100755
--- a/t/t7300-clean.sh
+++ b/t/t7300-clean.sh
@@ -788,4 +788,28 @@ test_expect_success 'traverse into directories that may have ignored entries' '
 	)
 '
 
+test_expect_success 'avoid traversing into untracked directories' '
+	test_when_finished rm -f output error trace.* &&
+	git init avoid-traversing-untracked-hierarchy &&
+	(
+		cd avoid-traversing-untracked-hierarchy &&
+
+		mkdir -p untracked/subdir/with/b &&
+		mkdir -p untracked/subdir/with/a &&
+		>untracked/subdir/with/a/random-file.txt &&
+
+		GIT_TRACE2_PERF="$TRASH_DIRECTORY/trace.output" \
+		git clean -ffdx
+	) &&
+
+	# Make sure we only visited into the top-level directory, and did
+	# not traverse into the "untracked" subdirectory since it was excluded
+	grep data.*read_directo.*directories-visited trace.output |
+		cut -d "|" -f 9 >trace.relevant &&
+	cat >trace.expect <<-EOF &&
+	 ..directories-visited:1
+	EOF
+	test_cmp trace.expect trace.relevant
+'
+
 test_done
-- 
2.35.1