Re: [PATCH] t5310-pack-bitmaps: skip JGit tests with SHA256

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

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Hi Peff,

On Wed, 18 Nov 2020, Jeff King wrote:

> On Wed, Nov 18, 2020 at 07:30:22PM +0100, SZEDER Gábor wrote:
>
> > > I wonder whether there is a way to change the `JGIT` prereq in a way
> > > that automagically will recognize a (future) SHA256-enabled JGit?
> > > Something like
> > >
> > > test_lazy_prereq JGIT '
> > > 	jgit --version &&
> > >         test_have_prereq !SHA1 ||
> > > 	test "$(git rev-list -n 1 HEAD)" = "$(jgit rev-list -n 1 HEAD)"
> > > '
> > >
> > > What do you think?
> >
> > I'm not sure.  It is surely a substantial effort to fully support
> > SHA256, and I suppose there will be JGit versions with only partial
> > support.  I'm worried that there will be versions that can already
> > read SHA256 objects, but can't read/write SHA256 pack bitmaps, or
> > can't transfer/negotiate SHA256 objects yet (for t5512), so even
> > though they could fulfill such a prereq test above, the test would
> > still fail.
>
> Yeah, it's likely we'll need to just match the output of "jgit
> --version". Since their support is hypothetical at this point, I think
> it makes sense to go with your original patch. It does mean we'll later
> have to remove the SHA1 prereq from those tests, but that's OK. It's not
> very many tests, and your commit message clearly explains what is going
> on.

It's not just removing the SHA-1 prereq, but testing for a new-enough
version.

This most likely entails adding a new test helper to `t/helper/` that
allows using `versioncmp()` via the command-line, with some clever way to
indicate the different outcomes, and then using that in a new prereq.

You know, if it was me, I would opt for the simpler (and future-proof)
solution I presented above. But hey, if that complex solution using
`versioncmp()` floats your boat, who am I to stop you.

Ciao,
Dscho