Re: [PATCH v3 1/4] t1400: avoid touching refs on filesystem

On Wed, Nov 11, 2020 at 07:58:38AM +0100, Patrick Steinhardt wrote:

The testcase t1400 exercises the git-update-ref(1) utility. To do so,
many tests directly read and write references via the filesystem,
assuming that we always use loose and/or packed references. While this
is true now, it'll change with the introduction of the reftable backend.

Convert those tests to use git-update-ref(1) and git-show-ref(1) where
possible. As some tests exercise behaviour with broken references and
neither of those tools actually allows writing or reading broken
references, this commit doesn't adjust all tests.

Do you want to mention the switch away from using HEAD in some tests
here?

+# Some of the tests delete HEAD, which causes us to not treat the current
+# working directory as a Git repository anymore. To avoid using any potential
+# parent repository to be discovered, we need to set up the ceiling directories.
+GIT_CEILING_DIRECTORIES="$PWD/.."
+export GIT_CEILING_DIRECTORIES

Do we still need this, now that we're not deleting HEAD? I think we do
still delete a branch via HEAD, but that should leave an unborn branch,
which is still a valid repo.

 test_expect_success "deleting current branch adds message to HEAD's log" '
-	test_when_finished "rm -f .git/$m" &&
+	test_when_finished "git update-ref -d $m" &&
 	git update-ref $m $A &&
 	git symbolic-ref HEAD $m &&
 	git update-ref -m delete-$m -d $m &&
-	test_path_is_missing .git/$m &&
+	test_must_fail git show-ref --verify -q $m &&
 	grep "delete-$m$" .git/logs/HEAD
 '

E.g., these ones should leave a valid repo (and must remain HEAD,
because it's special for reflogging).

-cp -f .git/HEAD .git/HEAD.orig
 test_expect_success 'delete symref without dereference' '
-	test_when_finished "cp -f .git/HEAD.orig .git/HEAD" &&
-	git update-ref --no-deref -d HEAD &&
-	test_path_is_missing .git/HEAD
+	git symbolic-ref SYMREF $m &&
+	git update-ref --no-deref -d SYMREF &&
+	test_must_fail git show-ref --verify -q SYMREF
 '

And now this one is safe. Good.

I wonder, though...is it still testing the same thing as the original?
This is not related to the use of SYMREF vs HEAD, but wouldn't show-ref
similarly fail if we had deleted $m, but left SYMREF in place (i.e., if
--no-deref didn't actually do anything)?

Perhaps this would be better:

  # confirm that the pointed-to ref is still there
  git show-ref --verify $m &&
  # but our symref is not
  test_must_fail git show-ref --verify SYMREF &&
  test_must_fail git symbolic-ref SYMREF

 test_expect_success 'delete symref without dereference when the referred ref is packed' '
-	test_when_finished "cp -f .git/HEAD.orig .git/HEAD" &&
 	echo foo >foo.c &&
 	git add foo.c &&
 	git commit -m foo &&
+	git symbolic-ref SYMREF $m &&
 	git pack-refs --all &&
-	git update-ref --no-deref -d HEAD &&
-	test_path_is_missing .git/HEAD
+	git update-ref --no-deref -d SYMREF &&
+	test_must_fail git show-ref --verify -q SYMREF
 '

Likewise here.

-Peff