Re: RFC: submodule terminology

From: Shawn O. Pearce <spearce@spearce.org>
Date: May 21, 2007, 06:52 UTC
Message-ID: <20070521065234.GM3141@spearce.org>
In-Reply-To: <1179729886.6187.15.camel@localhost>

Raimund Bauer <ray007@gmx.net> wrote:

Show 11 quoted lines

> On Sun, 2007-05-20 at 15:59 -0700, Junio C Hamano wrote:
> > I was wondering if we can get away by just calling them
> > "projects", "projects containd in the superproject", etc., as I
> > tend to agree with Linus, who used the term "superproject
> > support" in his talk, that this is not really about creating
> > "subproject" which are somehow different from ordinary projects,
> > but more about supporting superprojects that can contain/point
> > at other projects, which we did not have before 1.5.2 happened.
> 
> The "super" or "sub" only comes from where in a hierarchy it is used.
> Somewhere in the middle of the hierarchy it would be both?

Yes.  Of course.

> I'd have said a repository can have many "modules" or "projects", and
> each of those can have several branches. A module can hold other
> modules, but from its POV also be part of a super-module (or
> superproject), we just have to take care to not build loops.

You cannot build a loop.  OK, let me rephrase:

I can build a loop where at one point in time project A uses project B as his subproject; then later I can have project B use project A as a subproject. That's a loop. But the commits themselves are not in a cycle. There is a specific version of A that requires a specific version of B, and there is a different version of B that requires an entirely different version of A.

This loop really just means we have to be smart about how we switch between versions of a project. Just like if B is required in one version of superproject A and not in another; when I switch back and forth in A I expect B to appear/disappear. And I expect it to work on an airplane, where network access to reclone B is not available (or is too costly). That means we have to "hide" B when its not needed.

If you can actually form a loop where version of A requires version of B and version of B requires the version of A that requires the version of B... that's a SHA-1 hash collision. If you can make them at will, you probably can make some good money illegally...

> Is my view of the world correct so far?

Yes.

-- 
Shawn.