From: Jeff King <firstname.lastname@example.org>
To: Johannes Schindelin <Johannes.Schindelin@gmx.de>
Cc: Johannes Schindelin via GitGitGadget <email@example.com>,
firstname.lastname@example.org, Junio C Hamano <email@example.com>
Subject: Re: [PATCH v2 1/1] config: work around bug with includeif:onbranch and early config
Date: Wed, 31 Jul 2019 19:12:57 -0400 [thread overview]
Message-ID: <20190731231257.GB1933@sigill.intra.peff.net> (raw)
On Thu, Aug 01, 2019 at 12:13:19AM +0200, Johannes Schindelin wrote:
> > This gets tricky, because some commands are intentionally avoiding the
> > normal lookup procedure (e.g., clone or init, and probably things like
> > upload-pack that want to enter another repo). So I think it is OK as
> > long as the early-config code is explicitly saying "and please look at
> > the refs in this specific direectory now", and it doesn't affect other
> > possible code paths that might look at refs. I _think_ that's what
> > you're suggesting above, but I just want to make sure (not that it
> > matters either way for this patch).
> I think we already have the `git clone` problem with
> `includeif.gitdir:`. AFAICT we _will_ discover a Git directory when
> cloning inside an existing Git worktree.
Yeah, I could well believe that. I think it's hard for the config code
to say what's the right think to do here. If I'm running "git clone"
from inside another repository, should I respect, say, an alias defined
in that repository's config? Probably. But should I find that alias
behind "includeif.gitdir"? I dunno. Maybe?
So I'm not 100% sure the current behavior is buggy. And mostly I'd be
happy to ignore it until somebody comes up with a compelling
(real-world) example either way.
> And as you say, there was no use case, and I would even contend that
> there still is no use case. In the cover letter, I tried to concoct
> something (using a branch-dependent pager) that sounds _really_
> far-fetched to even me.
Yeah. I'd be totally fine if we left it with your fix here and nobody
ever found time to work on this. :)
> > > - const char *refname = resolve_ref_unsafe("HEAD", 0, NULL, &flags);
> > > + const char *refname = !the_repository || !the_repository->gitdir ?
> > > + NULL : resolve_ref_unsafe("HEAD", 0, NULL, &flags);
> > I think the_repository is always non-NULL.
> No, it totally can be `NULL`. I know because my first version of the
> patch did not have that extra check, and `git help -a` would segfault
> outside a Git worktree when I had an `includeif.onbranch:` in my
Hrm. But common-main calls initialize_the_repository(), which points it
at &the_repo. And I can't find any other assignments. So how does it
become NULL? And is every caller of have_git_dir() at risk of
Ah, I see. I think it is that trace2 reads the configuration very early.
I think we ought to do this:
diff --git a/common-main.c b/common-main.c
index 582a7b1886..89fd415e55 100644
@@ -39,14 +39,14 @@ int main(int argc, const char **argv)
result = cmd_main(argc, argv);
or possibly even move the trace2 bits to the very end of that function.
The point of common-main is to do very basic setup. Doing tentative repo
discovery and config reading there at all is surprising to me, to say
the least. But I think we can at least make sure the library code is
> > The way similar sites check this is withV
> > "!startup_info->have_repository" or have_git_dir(). The early-config
> > code uses the latter, so we should probably match it here.
> Quite frankly, I'd rather not. At this point, it is not important
> whether or not we discovered a Git directory, but whether or not we have
> populated a dereference'able `the_repository`. Those are two different
What I'm concerned about it is whether there are cases where
the_repository->gitdir is NULL, but we _could_ still look up refs. I.e.,
why is the rest of the config code using have_git_dir(), and why is this
code path special?
Again, I _think_ we might be able to get rid of have_git_dir() now. Back
when it was introduced get_git_dir() did lazy setup, and these days it
looks like it's just peeking at the_repository->gitdir. But it makes
sense to me for this fix to be consistent with the surrounding code, and
then to investigate have_git_dir() separately.
> > Side note: I suspect there are some cleanup opportunities. IIRC, I had
> > to add have_git_dir() to cover some cases where $GIT_DIR was set but
> > we hadn't explicitly done a setup step, but there's been a lot of
> > refactoring and cleanup in the initialization code since then. I'm not
> > sure if it's still necessary.
> Yeah, well, I am not necessarily certain that we always ask the right
> questions, such as asking whether we found a startup repository when we
> need, in fact, to know whether `the_repository->refs` would cause a
> segmentation fault because we would dereference a `NULL` pointer ;-)
If there are cases where startup_info->have_repository is non-zero but
we'd segfault, then I think that's a bug that is going to affect more
spots than this, and we need to investigate and fix. But I don't think
that is the case. We should only be setting it after calling
set_git_dir(), and poking at the current sites which set that leads me
to believe this is true.
next prev parent reply other threads:[~2019-07-31 23:13 UTC|newest]
Thread overview: 17+ messages / expand[flat|nested] mbox.gz Atom feed top
2019-07-31 19:53 [PATCH 0/1] Make the includeif:onbranch feature more robust Johannes Schindelin via GitGitGadget
2019-07-31 19:53 ` [PATCH 1/1] config: work around bug with includeif:onbranch and early config Johannes Schindelin via GitGitGadget
2019-07-31 21:37 ` Junio C Hamano
2019-07-31 20:06 ` [PATCH v2 0/1] Make the includeif:onbranch feature more robust Johannes Schindelin via GitGitGadget
2019-07-31 20:06 ` [PATCH v2 1/1] config: work around bug with includeif:onbranch and early config Johannes Schindelin via GitGitGadget
2019-07-31 22:02 ` Jeff King
2019-07-31 22:13 ` Johannes Schindelin
2019-07-31 23:12 ` Jeff King [this message]
2019-08-01 0:49 ` Jeff King
2019-08-01 17:24 ` Jeff Hostetler
2019-08-06 12:26 ` [PATCH 0/3] the_repository initialization cleanup Jeff King
2019-08-06 12:26 ` [PATCH 1/3] t1309: use short branch name in includeIf.onbranch test Jeff King
2019-08-06 12:27 ` [PATCH 2/3] common-main: delay trace2 initialization Jeff King
2019-08-06 12:27 ` [PATCH 3/3] config: stop checking whether the_repository is NULL Jeff King
2019-08-06 12:49 ` Jeff King
2019-08-08 19:48 ` Johannes Schindelin
2019-08-06 12:56 ` [PATCH v2 1/1] config: work around bug with includeif:onbranch and early config Jeff King
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