Re: nd/merge-quit, was Re: What's cooking in git.git (May 2019, #01; Thu, 9)

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

Hi,

On Mon, 13 May 2019, Johannes Schindelin wrote:

> On Fri, 10 May 2019, Duy Nguyen wrote:
>
> > On Fri, May 10, 2019 at 3:54 AM Johannes Schindelin
> > <Johannes.Schindelin@gmx.de> wrote:
> > >
> > > Hi Junio & Duy,
> > >
> > > On Thu, 9 May 2019, Junio C Hamano wrote:
> > >
> > > > * nd/merge-quit (2019-05-07) 2 commits
> > > >  - merge: add --quit
> > > >  - merge: remove drop_save() in favor of remove_merge_branch_state()
> > > >
> > > >  "git merge" learned "--quit" option that cleans up the in-progress
> > > >  merge while leaving the working tree and the index still in a mess.
> > > >
> > > >  Hmph, why is this a good idea?
> > >
> > > It also seems to work *only* on Linux. At least the tests break on macOS
> > > and on Windows:
> > >
> > > https://dev.azure.com/gitgitgadget/git/_build/results?buildId=8313&view=ms.vss-test-web.build-test-results-tab
> >
> > Sorry I have no idea what the problem is. That's basically the same as
> > the 'merge detects mod-256 conflicts (recursive)' test earlier but
> > with rerere enabled. It does not even look like some leftover rerere
> > records accidentally fix the conflict.
> >
> > I tried with a case-insensitive filesytem (on linux) and with
> > --valgrind, no problem found. Travis on pu seemed ok with t7600 on
> > mac.
> >
> > One difference I notice is the the failed test looks like it found the
> > wrong merge base
> >
> > found 1 common ancestor:
> > c4c4222 commit 1
> >
> > while my tests have "commit 0" as the base. "git log --graph
> > --oneline" indicates "commit 1" is the wrong base.
> >
> > Something is wrong with the merge code (this has not even reached the
> > new --quit code). I could change the setup steps to be more stable,
> > using a simpler commit history, but this looks like something we
> > should find and fix.
>
> Yeah... someone should look at this... Someone. But who?
>
> :-)
>
> Well, since you seemed quite reluctant to figure out why your patches fail
> the test suite, and since we're about to enter the -rc0 phase (where we
> all spend all of our time to hammer out the next version, right? Right?),
> I figured out I better look into it before nobody does.
>
> Turns out that the culprit is not even hard to figure out. All I had to do
> is to compare, carefully, the logs from the Azure Pipelines and from a
> local run in a local Ubuntu.
>
> It has nothing to do with our merge code. There might be bugs, but this
> breakage is safely in this here patch series: the test case you introduced
> relies on side effects.
>
> Namely, when test cases 51 and 52 are skipped because of a missing GPG
> prerequisite [*1*], and those two are obviously required to run for the
> `git merge to fail in your test case, as you can very easily verify by
> downloading the artifact containing the `trash directory.t7600-merge`
> directory and re-running the last steps on Linux (where the `git -c
> rerere.enabled=true merge master` *succeeds*).

I should have posted the link, as it may not be totally obvious where you
can download artifacts:

https://dev.azure.com/mseng/AzureDevOps/_build/results?buildId=9464474&view=artifacts

Ciao,
Johannes

> In fact, you can very, very easily emulate the whole situation on your box
> by running:
>
> 	sh t7600-merge.sh -i -v -x --run=1-50,53-59
>
> And then you can fix your test case so that it does not need to rely on
> test cases that may, or may not, have run previously.
>
> Ciao,
> Johannes
>
> Footnote *1*: GNU Privacy Guard is not actually missing from Git for
> Windows' SDK, quite to the contrary. But it fails to start a gpg-agent due
> to the fact that we pass a `--homedir` that contains a colon, something
> that is totally expected on Windows, and at the same something that GNU
> Privacy Guard totally cannot handle.
>
>