Re: [PATCH] Make some commit hashes in tests reproducible

[Han-Wen Nienhuys <hanwen@google.com>]

On Tue, Jul 7, 2020 at 9:50 PM Junio C Hamano <gitster@pobox.com> wrote:
>
> "Han-Wen Nienhuys via GitGitGadget" <gitgitgadget@gmail.com> writes:
>
> > From: Han-Wen Nienhuys <hanwen@google.com>
> >
> > Adds test_tick to t5801-remote-helpers.sh and t3203-branch-output.sh
>
> That can be read from the patch.  Also the subject tells us a half
> of what you want to achieve with this change (by the way, your
> subject is malformatted and lacks the <area>: prefix; perhaps
> "[PATCH] tests: make commit object names reproducible" or something),
> but the readers are left hanging without knowing what motivated the
> change.  Do any test pieces in these scripts change their behaviour
> based on what exact object names are assigned to them, making them
> flaky and hard to test, and if so which one and in what way?

You're right, I forgot to provide a piece of the puzzle. These tests
have been failing either legitimately or flakily with reftable.

I built a GIT_DEBUG_REFS functionality, which dumps ref backend
interactions onto stderr. This should be reworked to use the tracing
functionality, but you can look at the patch in my reftable series.

When a test fails with reftable, the easiest way to debug is running
it both with and without GIT_DEBUG_REFS=1, and running a diff on the
output.

This needs the commit SHA1s to be deterministic, or the SHA1s will
generate spurious diffs.

I agree with Jeff, that a more structural approach to making sha1s
deterministic would be preferable.

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Han-Wen Nienhuys - Google Munich
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