t7300: add testcase showing unnecessary traversal into ignored directory

The PNPM package manager is apparently creating deeply nested (but
ignored) directory structures; traversing them is costly
performance-wise, unnecessary, and in some cases is even throwing
warnings/errors because the paths are too long to handle on various
platforms.  Add a testcase that checks for such unnecessary directory
traversal.

Signed-off-by: Elijah Newren <newren@gmail.com>
Signed-off-by: Junio C Hamano <gitster@pobox.com>

diff --git a/t/t7300-clean.sh b/t/t7300-clean.sh
index a74816ca8b466c789c3bc8b17e629d5edcbb25e9..07e8ba2d4b8558b6e1aa39f2921a277b736079f5 100755 (executable)
--- a/t/t7300-clean.sh
+++ b/t/t7300-clean.sh
@@ -746,4 +746,27 @@ test_expect_success 'clean untracked paths by pathspec' '
        test_must_be_empty actual
 '
 
+test_expect_failure 'avoid traversing into ignored directories' '
+       test_when_finished rm -f output error trace.* &&
+       test_create_repo avoid-traversing-deep-hierarchy &&
+       (
+               cd avoid-traversing-deep-hierarchy &&
+
+               mkdir -p untracked/subdir/with/a &&
+               >untracked/subdir/with/a/random-file.txt &&
+
+               GIT_TRACE2_PERF="$TRASH_DIRECTORY/trace.output" \
+               git clean -ffdxn -e untracked
+       ) &&
+
+       # 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