Re: [PATCH] Makefile: generate 'git' as 'cc [...] -o git+ && mv git+ git'

[Jeff King <peff@peff.net>]

On Mon, Mar 08, 2021 at 01:38:32PM +0100, Ævar Arnfjörð Bjarmason wrote:

> >> Change the compilation of the main 'git' binary to not have the CC
> >> clobber 'git' in-place. This means that e.g. running the test suite
> >> in-place and recompiling won't fail whatever tests happen to be
> >> running for the duration of the binary being regenerated.
> >
> > I am not sure why I would want to support the workflow this is
> > trying to help.
> 
> Because it also allows me and others to do more testing on patches to
> git.git.
> 
> If I'm working on a patch to e.g. git-fsck I might be doing
> edit->save->some-tests, where "some-tests" are a subset of the test
> suite I think is relevant to fsck.
> 
> But after doing N commits with passing tests I might notice that some
> other part of the test suite I didn't expect to have anything to do with
> fsck broke because I wasn't running that test.
> 
> I wasn't running that test because I'm not going to wait 10-15 minutes
> for it to run while actively editing, but will wait 30s-1m for 10-50
> test files to run.
> 
> So I can also have the full test suite running in a loop in some side
> window that'll give me a headsup if the "while do-full-tests; [...]"
> loop breaks, at which point I'm likely to investigate it sooner than
> otherwise, and not waste time going down the wrong path.
> 
> You can of course do that now, but it requires having a worktree on the
> side or whatever, which isn't always ideal (sometimes I'd like to have
> these tests on uncommitted changes).

I don't always use it, but I have a "ci" script[1] that just runs the
test on each individual commit in a loop. The interesting things about
it (beyond a simple loop) are:

  - it operates in a worktree (that copies the config.mak from the main
    worktree if necessary).

  - it uses Michael Haggerty's git-test[2] to memoize results for a given
    tree. That makes it reasonable to leave running in the background,
    where it will only use CPU when there's something useful to do.
    I also use git-test for "git rebase -x", so a final "is each commit
    OK" check usually runs instantly, because the results are cached.

  - it uses inotifywait to decide when HEAD has been updated. This is
    mostly a fun hack. It could also just poll every 10 seconds or
    whatever.

  - it triggers a custom command when the tests fail. I can share my
    sad-trombone.wav with you if you need. ;)

Your mention of 10-15 minutes makes me wonder why your system is so
slow, though. I generally run the whole suite (minus cvs/svn/p4 bits) in
under a minute. I know it's _much_ slower on Windows, but I didn't think
that was your platform.

(In general, I'm mildly negative on your patch here. I have definitely
run into this myself, but I think having the test suite loudly complain
is a good way to remind you that you have not in fact run the whole
suite on a given build).

[1] https://github.com/peff/git/blob/meta/ci
[2] https://github.com/mhagger/git-test

-Peff