Re: [PATCH 1/2] store submodule in common dir

From: Stefan Beller <sbeller@google.com>
Date: Aug 14, 2018, 23:23 UTC
Message-ID: <CAGZ79kbhwyMTmnwhuaOLOnffaEX_G1L7dR=qvV6Rjncq0POq7g@mail.gmail.com>
In-Reply-To: <xmqqo9e4y2gr.fsf@gitster-ct.c.googlers.com>

On Tue, Aug 14, 2018 at 4:04 PM Junio C Hamano <gitster@pobox.com> wrote:

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>
> Stefan Beller <sbeller@google.com> writes:
>
> > Signed-off-by: Stefan Beller <sbeller@google.com>
> > ---
> >  path.c | 1 +
> >  1 file changed, 1 insertion(+)
> >
> > On Tue, Aug 14, 2018 at 3:27 PM Joakim Tjernlund <Joakim.Tjernlund@infinera.com> wrote:
> >>
> >> I am trying to create 3 submodules from the same git repo, each pointing to a different branch.
> >> Since the repo is somewhat large, I don't want the 3 submodules to clone the same repo 3
> >> times, I want one clone and then have the 3 submodules to point to different commits.
> >>
> >> Is this possible? If not, could it be added?
> >
> > yup.
> >
> > According to recent discussions, it would be just this patch.
> > (plus some unspecified amount of work, TBD).
> >
> > I thought about proposing something proper later, but here is the WIP patch.
> >
> > Thanks,
> > Stefan
>
> My understanding of what Joakim wants to do is to have a top-level
> project that has three subdirectories, e.g. kernel/v2.2, kernel/v2.4
> and kernel/v2.6, each of which is a submodule that houses these
> versions of Linux kernel source, but only clone Linus's repository
> (as the up-to-late tree has all the necessary history to check out
> these past development tracks).  And that should be doable with
> just the main checkout, without any additional worktree (it's just
> the matter of having .git/modules/kernel%2fv2.6/ directory pointed
> by two symlinks from .git/modules/kernel%2fv2.[24], or something
> like that).

Ah! I misunderstood due to fast reading.

For that I think you are interested in the feature added in d92a39590d1 (Add --reference option to git submodule., 2009-05-04), i.e. both the update and add command take the --reference flag that can be pointed at another repository such as an outside clone of these three submodules, so some deduplication will be performed.

Show 7 quoted lines

> Isn't "common_dir" stuff used to decide if each of separate
> "worktree" instance (of the superproject) shares ".git/$stuff"
> with each other?
>
> Unless I am grossly misinterpreting the original question, I fail to
> see how changing .git/modules to be shared across worktrees possibly
> affects anything.  I am puzzled...

I did misunderstand grossly.

Stefan