Re: Rebase-via-merge behavior difference between Linux and Windows

From: Bryan Turner <bturner@atlassian.com>
Date: Apr 2, 2020, 01:15 UTC
Message-ID: <CAGyf7-FTNOgDbWEoniaOWueWGXwH6=0gj_FzDqP35422vxhYEA@mail.gmail.com>
In-Reply-To: <CABPp-BFDx2j5Kf584Myb6wuEq5G7wbogJ2vos8OTDsh+ySfk8w@mail.gmail.com>

On Tue, Mar 31, 2020 at 11:35 PM Elijah Newren <newren@gmail.com> wrote:

Show 29 quoted lines

>
> On Tue, Mar 31, 2020 at 4:25 PM Bryan Turner <bturner@atlassian.com> wrote:
> >
> > Using our merge test repository[1], one such test performs the following steps:
> > * Unzip bare repository
> > * `git clone --shared -b branch_that_differ_by_empty_commit_trgt
> > <unzipped> rebase-test`
> > * `git rebase -q --no-verify 7549846524f8aed2bd1c0249993ae1bf9d3c9998
> > 298924b8c403240eaf89dcda0cce7271620ab2f6`
> >
> > 298924b8c40 is an empty commit (i.e. `git commit --allow-empty`), and
> > is the only commit not already reachable from 7549846524f.
> >
> > On Linux, when this test completes, "HEAD" in "rebase-test" is
> > 7549846524f because the empty commit was discarded. This is the
> > expected behavior. On Windows, "HEAD" is a new empty commit, which
> > causes our test to fail.
>
> I don't have a Windows box to test, but it's good that you are seeing
> the correct behavior there.  I do have a Linux box, and cannot
> duplicate the behavior you state, even downloading the zip you
> mentioned and following your steps to reproduce.  Actually, I did
> reproduce that behavior the first time because I was accidentally
> using git-2.25.0.  But with git-2.26.0 on Linux, I see a new empty
> commit after rebasing, as expected.
>
> Is there any chance you accidentally ran with an older git version
> when on Linux?  If you really were using git 2.26.0 on Linux...then
> I'm totally confused at how you got that behavior.

I went back through our build logs and confirmed that we _are_ running Git 2.26 (phew). I then set up a local Git 2.26 environment and...it produced the same new behavior as 2.26 on Windows (so the correct behavior, per the documented changes).

At that point I dug further into our builds and found that while we were using the right Git version, we _weren't_ running all the same tests on Linux and Windows. So the successful build on Linux was not because the tests pass--I've adjusted the builds and confirmed that the tests _don't_ pass--but rather because the relevant tests weren't being run at all.

Very sorry for wasting your time, Elijah. I should have looked into our builds more closely to verify they were running the same tests before I took the question to the list.

Best regards, Bryan Turner