Re: Avery Pennarun's git-subtree?

From: Avery Pennarun <apenwarr@gmail.com>
Date: Jul 27, 2010, 18:28 UTC
Message-ID: <20100727182841.GA25124@worldvisions.ca>
In-Reply-To: <AANLkTimQywtn-0Fcr-ceLeHGeSBNROt+T=K+TowF_u5h@mail.gmail.com>

On Mon, Jul 26, 2010 at 09:41:42AM -0700, Linus Torvalds wrote:

Show 16 quoted lines

> On Mon, Jul 26, 2010 at 9:37 AM, Marc Branchaud <marcnarc@xiplink.com> wrote:
> >
> > I think I should mention one aspect of what we're doing, which is that a lot
> > of our submodules are based on external code, and that we occasionally need
> > to modify or customize some of that code.  So it's quite nice for us to
> > maintain private git mirrors of the external repos, with our own private
> > branches that contain our modifications.  Although we want to get much of our
> > changes incorporated into the upstream code bases, upstream release cycles
> > are rarely in sync with ours.
> 
> THIS.
> 
> This is why I always thought that submodules absolutely have to be
> commits, not trees. It's why the git submodule data structures are
> done the way they are. Anything that makes the submodule just a tree
> is fundamentally broken, I think.

I agree completely. The major failing of git-subtree is that it uses tree->tree links instead of tree->commit links.

This was necessary only because git fundamentally *mistreats* tree->commit links: it refuses to push or fetch through them automatically. That is, when I fetch a superproject that has a tree->commit link in it, git won't fetch the subproject's history starting at the targeted commit, even if the remote repo *has* that history. And if I make a patch to the subproject, pushing the superproject won't push that patch.

Have fun,

Avery