Re: [PATCH] remote-curl: fix clone on sha256 repos

[Jeff King <peff@peff.net>]

On Tue, May 11, 2021 at 04:47:28PM +0200, Ævar Arnfjörð Bjarmason wrote:

> 
> On Tue, May 11 2021, Eric Wong wrote:
> 
> > I'm not very familiar with the way some of this stuff works, but
> > the patch below seems to fix clone for me.
> 
> Me neither, but it seems that whatever issue we have here we've got a
> big blind spot in our test suite.
> 
> GIT_SMART_HTTP in the environment will be ignored by test-lib.sh,
> manually changing the code to use it leads to a lot of test failures,
> some are definitely expected (incompatible server responses), but some
> might not be...

There are specific dumb-http tests in t5550. And I think we can and do
run the suite with GIT_TEST_DEFAULT_HASH=sha256. But I suspect that
covers up the problem. If I understand the problem correctly, it comes
about when the client thinks the default hash is sha1, but the server is
sha256. Whereas GIT_TEST_DEFAULT_HASH affects _both_ sides.

So I think we'd want interop tests in t5550 that specifically create a
sha256 server and access it with a sha1 client (and possibly vice
versa).

It would be nice if there was a way to use an environment variable like
GIT_TEST_DEFAULT_HASH to mean "be hash X on the server, but Y on the
client". But I don't think we can easily do that. The "git init" command
which is used to create a repo that is later used for server access
doesn't _know_ that's what it's being used for. Possibly we could have
an extra variable that instructs git-clone to use a separate default
hash. And then:

  GIT_TEST_DEFAULT_HASH=sha256 \
  GIT_TEST_CLONE_DEFAULT_HASH=sha1 \
  make test

might possibly trigger some interesting cases.

-Peff