[PATCH] status: add a failing test showing a core.untrackedCache bug

From: Ævar Arnfjörð Bjarmason <avarab@gmail.com>
Date: Dec 22, 2017, 14:00 UTC
Message-ID: <20171222140032.21180-1-avarab@gmail.com>

The untracked cache gets confused when a directory is swapped out for a symlink to another directory. Whatever files are inside the target of the symlink will be incorrectly shown as untracked. This issue does not happen if the symlink links to another file, only if it links to another directory.

A stand-alone testcase for copying into a terminal:

    (
        rm -rf /tmp/testrepo &&
        git init /tmp/testrepo &&
        cd /tmp/testrepo &&
        mkdir x y &&
        touch x/a y/b &&
        git add x/a y/b &&
        git commit -msnap &&
        git rm -rf y &&
        ln -s x y &&
        git add y &&
        git commit -msnap2 &&
        git checkout HEAD~ &&
        git status &&
        git checkout master &&
        sleep 1 &&
        git status &&
        git status
    )

This will incorrectly show y/a as an untracked file. Both the "git status" call right before "git checkout master" and the "sleep 1" after the "checkout master" are needed to reproduce this, presumably due to the untracked cache tracking on the basis of cached whole seconds from stat(2).

When git gets into this state, a workaround to fix it is to issue a one-off:

    git -c core.untrackedCache=false status

Signed-off-by: Ævar Arnfjörð Bjarmason <avarab@gmail.com>
---
 t/t7063-status-untracked-cache.sh | 45 +++++++++++++++++++++++++++++++++++++++
 1 file changed, 45 insertions(+)

diff --git a/t/t7063-status-untracked-cache.sh b/t/t7063-status-untracked-cache.sh
index e5fb892f95..7cf1e2c091 100755
--- a/t/t7063-status-untracked-cache.sh
+++ b/t/t7063-status-untracked-cache.sh
@@ -22,6 +22,12 @@ avoid_racy() {
 	sleep 1
 }
 
+status_is_clean() {
+	>../status.expect &&
+	git status --porcelain >../status.actual &&
+	test_cmp ../status.expect ../status.actual
+}
+
 test_lazy_prereq UNTRACKED_CACHE '
 	{ git update-index --test-untracked-cache; ret=$?; } &&
 	test $ret -ne 1
@@ -683,4 +689,43 @@ test_expect_success 'untracked cache survives a commit' '
 	test_cmp ../before ../after
 '
 
+test_expect_success 'teardown worktree' '
+    cd ..
+'
+
+test_expect_success 'setup worktree for symlink test' '
+	git init worktree-symlink &&
+	cd worktree-symlink &&
+	git config core.untrackedCache true &&
+	mkdir one two &&
+	touch one/file two/file &&
+	git add one/file two/file &&
+	git commit -m"first commit" &&
+	git rm -rf one &&
+	ln -s two one &&
+	git add one &&
+	git commit -m"second commit"
+'
+
+test_expect_failure '"status" after symlink replacement should be clean with UC=true' '
+	git checkout HEAD~ &&
+	status_is_clean &&
+	status_is_clean &&
+	git checkout master &&
+	avoid_racy &&
+	status_is_clean &&
+	status_is_clean
+'
+
+test_expect_success '"status" after symlink replacement should be clean with UC=false' '
+	git config core.untrackedCache false &&
+	git checkout HEAD~ &&
+	status_is_clean &&
+	status_is_clean &&
+	git checkout master &&
+	avoid_racy &&
+	status_is_clean &&
+	status_is_clean
+'
+
 test_done

-- 
2.15.1.424.g9478a66081