Re: [PATCH 1/2] t/perf: time rev-list with UNINTERESTING commits

[Jeff King <peff@peff.net>]

On Mon, Jan 20, 2014 at 11:32:12PM +0100, Thomas Rast wrote:

> > This is bad to be touching the repo and assuming it is non-bare. For
> > some reason I assumed that the perf suite made a copy of the repo, but
> > it doesn't. If you point to a bare repo via GIT_PERF_REPO, this part of
> > the test fails.
> 
> It does make a copy, but with cp -Rl.  I haven't actually ever tried
> what happens if you point it at a bare though.  It *should* fail because
> it tries to cd $repo/.git, but if that was itself bare...

Oh, hmph. I checked my linux repo, which I had used as GIT_PERF_REPO,
and noticed that it had the test commit in its reflog. But I forgot that
is because I did the test manually there right before writing up the
t/perf script!  So yes, it copies, and it's totally fine to be modifying
the repo.

Bare repos seem to work just fine for me. It looks like we use `git
rev-parse --git-dir` to get the source, and then copy that to `.git` in
the temporary directory. So that works fine either way, and we do have a
directory available as the working dir. But of course the config from
the bare repo says `core.bare = true`, so some commands will bail.

We could perhaps just set GIT_WORK_TREE in the perf scripts, which I
believe would override the bare setting in the .git/config. And then we
know the repos will be consistently non-bare.

Whether we do that or not, I think the update I posted is preferable, as
it reproduces the problem in a much simpler manner.

-Peff