Re: [RFC/PATCH 0/7] Rework git core for native submodules

From: Linus Torvalds <torvalds@linux-foundation.org>
Date: Apr 4, 2013, 19:04 UTC
Message-ID: <CA+55aFyQwJfiYo06y1bRNpKT6wOquhG9a9M_4YvLG_UT3b34-w@mail.gmail.com>
In-Reply-To: <CALkWK0nNjvV5VGvT_eaubFoOhMnJ-N8FECAayd5A2K3BzeRh6Q@mail.gmail.com>

On Thu, Apr 4, 2013 at 11:52 AM, Ramkumar Ramachandra <artagnon@gmail.com> wrote:

Show 16 quoted lines

>
> 1. upstream_url: this records the upstream URL.  No need to keep a .gitmodules.
>
> 2. checkout_rev: this records the ref to check out the submodule to.
> As opposed to a concrete SHA-1, this allows for more flexibility; you
> can put refs/heads/master and have truly floating submodules.
>
> 3. ref_name: this specifies what name the ref under
> refs/modules/<branch>/ should use.
>
> 4. floating: this bit specifies whether to record a concrete SHA-1 in
> checkout_rev.
>
> 5. statthrough: this bit specifies whether git should stat() through
> the worktree.  We can turn it off on big repositories for performance
> reasons.

So the thing is (and this was pretty much the original basis for .gitmodules) that pretty much *all* of the above fields are quite possibly site-specific, rather than globally stable.

So I actually conceptually like (and liked) the notion of a link object, but I just don't think it is necessarily practically useful, exactly because different installations of the *same* supermodule might well want to have different setups wrt these submodule fields.

My gut feel is that yes, .gitmodules was always a bit of a hack, but it's a *working* hack, and it does have advantages exactly because it's more fluid than an actual git object (which by definition has to be set 100% in stone). If there are things you feel it does wrong (like the "git add" bug that is being discussed elsewhere), I wonder if it's not best to at least try to fix/extend them in the current model. The features you seem to be after (ie that whole floating/refname thing) don't seem fundamentally antithetical to the current model (a "commit" SHA1 of all zeroes for floating, with a new refname field in .submodules? I dunno)..

                  Linus