Re: in case you want a use-case with lots of submodules

From: Stefan Beller <sbeller@google.com>
Date: Jun 19, 2017, 19:30 UTC
Message-ID: <CAGZ79kZhj31eBYnboyxDLuFp1ceeqk8kj0nrnQaCmpRJCVFU4w@mail.gmail.com>
In-Reply-To: <20170619155924.7ra2vwvaelr2yj2v@hopa.kiewit.dartmouth.edu>

On Mon, Jun 19, 2017 at 8:59 AM, Yaroslav Halchenko <yoh@onerussian.com> wrote:

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> Hi All,
>
> On a recent trip I've listened to the git minutes podcast episode and
> got excited to hear  Stefan Beller (CCed just in case) describing
> ongoing work on submodules mechanism.  I got excited, since e.g.
> performance improvements would be of great benefit to us too.

If you're mostly interested in performance improvements of the status quo (i.e. "make git-submodule fast"), then the work of Prathamesh Chavan (cc'd) might be more interesting to you than what I do. He is porting git-submodule (which is mostly a shell script nowadays) to C, such that we can save a lot of process invocations and can do processing within one process.

> In our project, http://datalad.org, git submodules is the basic
> mechanism to bring multiple "datasets" (mix of git and git-annex'ed
> repositories)  under the same roof so we could non-ambiguously
> version them all at any level.

Cool, glad to here submodules being useful. :)

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> http://datasets.datalad.org ATM provides quite a sizeable (ATM 370
> repositories, up to 4 levels deep) hierarchy of git/git-annex
> repositories all tied together via git submodules mechanism.  And as the
> collection grows, interactions with it become slower, so additional
> options (such as --ignore-submodules=dirty  to status) become our
> friends.

I am not as much concerned about the 370 number than about the 4 layers of nesting. In my experience the nested submodule case is a little bit error prone and the bug reports are not as frequent as there are not as many users of nesting, yet(?)

In a neighboring thread on the mailing list we have a discussion on the usefulness of being on branches than in detached HEAD in the submodules. https://public-inbox.org/git/0092CDD27C5F9D418B0F3E9B5D05BE08010287DF@SBS2011.opfingen.plc2.de/

This would not break non-ambiguously, rather it would add ease of use.

> So I thought to share this as a use-case happen you need more
> motivation or just a real-case test-bed for your work.  And thank
> you again for making Git even Greater.

Thanks for the motivation. :)

> P.S. Please CCme in your replies (if any), I am not on the list
>
> With best regards,

Cheers, Stefan