On Mon, Nov 09, 2020 at 11:48:20AM -0800, Junio C Hamano wrote: > Patrick Steinhardt writes: > > diff --git a/t/t1400-update-ref.sh b/t/t1400-update-ref.sh > > index 4c01e08551..957bef272d 100755 > > --- a/t/t1400-update-ref.sh > > +++ b/t/t1400-update-ref.sh > > @@ -14,6 +14,12 @@ n=$n_dir/fixes > > outside=refs/foo > > bare=bare-repo > > > > +# Some of the tests delete HEAD, which causes us to not treat the current > > +# working directory as a Git repository anymore. To avoid using any potential > > +# parent repository to be discovered, we need to set up the ceiling directories. > > +GIT_CEILING_DIRECTORIES="$PWD/.." > > +export GIT_CEILING_DIRECTORIES > > + > > Interesting. The current tests do not need to do this because the > HEAD-less broken state is transitory and is corrected without using > "git" at all (e.g. echoing a valid value into .git/HEAD), I presume? Correct. > > @@ -80,26 +86,26 @@ test_expect_success "fail to delete $m (by HEAD) with stale ref" ' > > test $B = $(git show-ref -s --verify $m) > > ' > > test_expect_success "delete $m (by HEAD)" ' > > - test_when_finished "rm -f .git/$m" && > > + test_when_finished "git update-ref -d $m" && > > git update-ref -d HEAD $B && > > - test_path_is_missing .git/$m > > + test_must_fail git show-ref --verify -q $m > > ' > > During the above test, we are on the branch ${m#refs/heads/}, so > "update-ref -d HEAD" is removing the underlying branch ref, making > it an unborn branch, without destroying the repository, so this is > perfectly sensible. > > This is a tangent, but what makes this test doubly interesting is > that "git update-ref -d HEAD" would have allowed us to make it a > non-repository if HEAD were detached, and it seems that we do not > require "--force" to do so. We probably should forbid removing HEAD > that id detached without "--force", which is such a destructive > operation. That'd make sense to me, yes. It also took me quite some time to actually figure out why tests were misbehaving when I converted it. Until I finally realized: this is not a Git repo anymore, and refs have now been modified directly in the real git.git repository. Just this morning I still found some invalid refs created by the test in git.git. > > cp -f .git/HEAD .git/HEAD.orig > > test_expect_success 'delete symref without dereference' ' > > test_when_finished "cp -f .git/HEAD.orig .git/HEAD" && > > git update-ref --no-deref -d HEAD && > > - test_path_is_missing .git/HEAD > > + test_must_fail git show-ref --verify -q HEAD > > ' > > This is an example of breaking the repository. I am not sure if the > test_must_fail is a good replacement--it would fail even if you say > "git show-ref --verify -q refs/heads/$branch" where $branch is a > name of a branch that exists, no? Right, it's not. We're not detecting HEAD deletion by means of checking that it doesn't exist anymore, but only detect it because the repo is not a repo anymore. Which would in fact cause most git commands to fail now. > For now, I think this is fine, but we'd probably clean it up so that > without --force update-ref would not corrupt the repository like > this. When used with --force, or before adding such a safety > measure, how we test if we successfully corrupted the repository is > an interesting matter. I'd say > > git update-ref --force --no-deref -d HEAD && > test_must_fail git show-ref --verify -q HEAD && > cp -f .git/HEAD.orig .git/HEAD && > git show-ref --verify -q "$m" > > to ensure that other than removing HEAD and corrupting the > repository, it did not cause permanent damage by removing the > underlying ref, perhaps. > > We may want to add some NEEDSWORK comment around such tests. I think the proper way to do the test would be to create a non-mandatory symref and delete it. That'd also be a nice preparation for the `--force` parameter already. > > test_expect_success 'delete symref without dereference when the referred ref is packed' ' > > @@ -208,7 +214,7 @@ test_expect_success 'delete symref without dereference when the referred ref is > > git commit -m foo && > > git pack-refs --all && > > git update-ref --no-deref -d HEAD && > > - test_path_is_missing .git/HEAD > > + test_must_fail git show-ref --verify -q HEAD > > ' > > Does this share the same issue as the above? Yup, it does. Patrick