Re: [PATCH] t1309: use a non-loaded branch name in the `onbranch` test cases

[Johannes Schindelin <Johannes.Schindelin@gmx.de>]

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Hi Ævar,

On Wed, 18 Nov 2020, Ævar Arnfjörð Bjarmason wrote:

> On Wed, Nov 18 2020, Johannes Schindelin via GitGitGadget wrote:
>
> > From: Johannes Schindelin <johannes.schindelin@gmx.de>
> >
> > The `onbranch` test cases in question do not actually want to include
> > anything; Instead, they want to verify that the `onbranch` code path
> > does not regress in the early-config case or in the non-Git case, where
> > the `onbranch` include is actually ignored.
>
> It's unclear to me what this patch is for & why it's needed.

Well, the entire idea of switching to a new default branch name is to
avoid using words that we know cause undue emotional harm. In the grand
scheme, therefore, I want to avoid having any mention of such words in our
test suite.

> Yesterday in your v2 27/27 series you sent a different one that changed
> this from s/master/main/g:
> https://lore.kernel.org/git/b8fa037791683b50c3efb01aa6ac0d3f7b888a2b.1605629548.git.gitgitgadget@gmail.com/
>
> That's on top of "next", but this one is on "master", the two would
> conflict, and the 02/27 one seems like the right thing to do.

Yeah, I hadn't made it clear yet at the time you wrote this that my
intention was to give in to your and Junio's suggestion to restrict the
`GIT_TEST_DEFAULT_INITIAL_BRANCH_NAME` assignments to _just_ the test
scripts that don't work with arbitrary default branch names.

I had hoped that mentioning gitgitgadget PR 762 (which is that 27-strong
patch series) would be indicator enough that I was in the process of
revamping it into a v3, and that this here patch is one part that I
separated out into its own patch.

> > Therefore, the actual branch name does not matter at all. We might just
> > as well avoid racially-charged names here.
>
> It seems to me the actual name matters a lot, and it must whatever the
> default branch name is.

Nope. Not at all. Because what we're exercising is the code paths when we
_don't_ have a branch name to work with.

In the non-Git case, this is trivial to see. There is not even a
repository! How can there be a branch?

In the early config case, it is too early to access the refs. I meant to
reference (but forgot) the commit 85fe0e800ca (config: work around bug
with includeif:onbranch and early config, 2019-07-31) because that
commit's commit message describes the catch-22 that is the reason why the
early config cannot see the current branch name (if any).

I should probably have thought of referencing 22932d9169f (config: stop
checking whether the_repository is NULL, 2019-08-06) for the second test
case, too.

So again, these two test cases do _not_ exercise the code path where
another config file is included. To the contrary, they try to prevent a
regression where `onbranch` would segfault in one case, and BUG in the
other (in both cases because the now-fixed code used to try to look at the
current branch name _anyway_).

> I.e. what the test is doing is producing intentionally broken config,
> and asserting that we don't read it at an early stage.
>
> Therefore if we regressed and started doing that the test wouldn't catch
> it, because the default branch name is "master", or "main" if/when that
> refs.c change lands, neither of which is "topic".

No, if we regressed, the code would start to throw a BUG, or a segfault,
respectively.

We never expect these two test cases to look at any branch name at all.

Ciao,
Dscho

> Maybe I'm missing something but it seems 58ebccb478 ("t1309: use short
> branch name in includeIf.onbranch test", 2019-08-06) and your own
> 85fe0e800c ("config: work around bug with includeif:onbranch and early
> config", 2019-07-31) which added the test support reading.
>
>
> > Signed-off-by: Johannes Schindelin <johannes.schindelin@gmx.de>
> > ---
> >     t1309: use a non-loaded branch name in the onbranch test cases
> >
> >     Just something I stumbled over while working on
> >     https://github.com/gitgitgadget/git/pull/762.
> >
> > Published-As: https://github.com/gitgitgadget/git/releases/tag/pr-791%2Fdscho%2Ft1309-onbranch-tests-v1
> > Fetch-It-Via: git fetch https://github.com/gitgitgadget/git pr-791/dscho/t1309-onbranch-tests-v1
> > Pull-Request: https://github.com/gitgitgadget/git/pull/791
> >
> >  t/t1309-early-config.sh | 4 ++--
> >  1 file changed, 2 insertions(+), 2 deletions(-)
> >
> > diff --git a/t/t1309-early-config.sh b/t/t1309-early-config.sh
> > index ebb8e1aecb..b4a9158307 100755
> > --- a/t/t1309-early-config.sh
> > +++ b/t/t1309-early-config.sh
> > @@ -91,11 +91,11 @@ test_expect_failure 'ignore .git/ with invalid config' '
> >
> >  test_expect_success 'early config and onbranch' '
> >  	echo "[broken" >broken &&
> > -	test_with_config "[includeif \"onbranch:master\"]path=../broken"
> > +	test_with_config "[includeif \"onbranch:topic\"]path=../broken"
> >  '
> >
> >  test_expect_success 'onbranch config outside of git repo' '
> > -	test_config_global includeIf.onbranch:master.path non-existent &&
> > +	test_config_global includeIf.onbranch:topic.path non-existent &&
> >  	nongit git help
> >  '
> >
> >
> > base-commit: e31aba42fb12bdeb0f850829e008e1e3f43af500
>
>
>