Re: git diff --submodule=diff and --stat/--dirstat/--name-only

[Marc Sune <marcdevel@gmail.com>]

Philippe,

Missatge de Philippe Blain <levraiphilippeblain@gmail.com> del dia
dj., 15 d’oct. 2020 a les 0:51:
>
> Hi Marc,
>
> > Le 14 oct. 2020 à 10:35, Marc Sune <marcdevel@gmail.com> a écrit :
> >
> > Philippe,
> >
> > Missatge de Philippe Blain <levraiphilippeblain@gmail.com> del dia
> > dc., 14 d’oct. 2020 a les 15:29:
> >>
> >> Hi Marc,
> >>
> >>> Le 14 oct. 2020 à 06:14, Marc Sune <marcdevel@gmail.com> a écrit :
> >>>
> >>> Hello all,
> >>>
> >>> First, thank you to the community for the great work. Worth saying it
> >>> from time to time, I think.
> >>>
> >>> I am dealing with a couple of big repositories that use git
> >>> submodules. They have nested submodules, and some of them are pretty
> >>> huge. I came across:
> >>>
> >>> git diff --submodule=diff
> >>>
> >>> Which is very handy for creating some tooling, but it's obviously slow
> >>> - in the order of tens of minutes in my case - for big diffs. I was
> >>> only interested in the list files that changed, in this particular
> >>> case, but:
> >>>
> >>> git diff --stat --submodule=diff
> >>>
> >>> doesn't seem to honour `--submodule=diff` and it doesn't go into the
> >>> submodule(s) nor recurses, of course. Other options like `--dirstat`
> >>> or `--name-only` seem to behave the same way.
> >>>
> >>> I've tried this v2.20.1 and the HEAD of master (d4a392452e) with the
> >>> same results. Is this a missing feature, a bug or is it just the
> >>> intended behaviour?
> >>>
> >>> Regards
> >>> marc
> >>
> >> This would indeed be useful. It's a missing feature, and so intended behaviour
> >> for the moment, I would say. It was discussed recently on the list [1] :
> >>
> >>
> >> [1] https://lore.kernel.org/git/20200924063829.GA1851751@coredump.intra.peff.net/t/#u
> >
> > Thank you for the pointer and the clarification.
> >
> > I am not sure extending `git diff` options (only) under
> > `--submodule=`, e.g. `--submodule=stat` is the way to go. It seems
> > redundant to me.
> >
> > I am wondering if it would make sense to have basic options of git
> > commands, e.g. `git diff --stat`, be honoured for submodules too, and
> > just control whether git commands should get in the submodule(s) or
> > not, and perhaps the depth of the recursion (optionally).
>
> Did you try `git submodule foreach` ? If you are scripting, you could do:
>
>     git diff --stat && git submodule foreach [--recursive] git diff --stat

Yes, ofc. There are multiple reasons for not using it in this specific
case I am facing (specially performance), but this is probably
offtopic.

>
> Although here the recursion is an all-or-nothing business.
>
> > For instance, I don't fully get the use-case(s) in which parts of the
> > output are --stat (supermodule) and submodules show something
> > different:
> >
> > git diff --stat --submodule=diff
> > git diff --stat --submodule=log
> >
> > Specially for log, this sounds to me like it should be under `git
> > log`, with the appropriate options.
>
> I think 'log' is useful; it's more descriptive then having just a hash,
> which is the default...
>
> > Perhaps you can shed some light on
> > the use-cases these combinations support.
> >
> > I would think something like:
> >
> > git diff --stat --submodule-follow
> > git diff --stat --submodule-follow-depth=4
> >
> > git diff --names-only --submodule-follow
> > git diff --dirstat --submodule-follow
> > and for other commands (some sort of header line should be printed to
> > note the history is under the submodule X):
> >
> > git log --submodule-follow
> > git log --submodule-follow-depth=4
> >
> > and of course allowing `--` modifier:
> >
> > git log --submodule-follow -- libs/library1
> >
> > would be easier to use.
>
> I'm not sure of the use case for these... The history
> of the submodule project can be seen with `git -C path/to/submodule log`
> (or just `cd` there and `git log`), and the history of the gitlink in the superproject
> with `git log -- path/to/submodule`...
>
> It does not really make sense to interleave the history of the superproject and
> the submodule in the same output, in my opinion at least.
>
> > Let me know if any of this resonates, and if some patches along these
> > lines would be welcomed
>
> I can't really answer that, I'm just a small time contributor :)

I will wait for some thoughts on the proposal, and to see if someone
can shed some light on the reasons why `--submodule=` option works the
way it does, today, in git diff.

Regards
marc

>
> > (might ask some help offlist).
>
> You should ask on the list, on the mentoring list, or on IRC (see [1]).
>
> [1] https://git-scm.com/docs/MyFirstContribution#getting-help
>
> Cheers,
> Philippe.
>