Re: git submodules

From: Shawn O. Pearce <spearce@spearce.org>
Date: Jul 29, 2008, 06:04 UTC
Message-ID: <20080729060449.GG11947@spearce.org>
In-Reply-To: <b3889dff0807282251t7096a8c9wf477cf4495749d34@mail.gmail.com>

Benjamin Collins <aggieben@gmail.com> wrote:

Show 14 quoted lines

> On Mon, Jul 28, 2008 at 4:40 PM, Avery Pennarun <apenwarr@gmail.com> wrote:
> >
> > > One irritating problem with submodules, is
> > > that when someone else commited, and that you git submodule update,
> > > you're on a detached head. Absolutely horrible.
> >
> > I think that roughly everyone agrees with the above statement by now.
> > It would also be trivial to fix it, if only we knew what "fix" means.
> > So far, I haven't seen any good suggestions for what branch name to
> > use automatically in a submodule, and believe me, I've been looking
> > for one :)
> 
> I disagree with this completely. I think the detached head is
> actually fantastic [...]

Ditto with Benjamin.  Detached head is a fantastic idea.

Show 11 quoted lines

> [...] because it tells you all the right things:
> a) the branch your submodule is on is ultimately irrelevant
> b) it reminds you that this is not your project.  It's part of your
> project managed in a special way by Git, but your project is in ..
> c) if you want to do work in this part of your project that comes from
> somewhere else, you need to be thoughtful about how you manage its
> branches.
> 
> I try to keep all my submodules on (no branch) as much as possible.
> In a way, I feel like that kind of relieves me of the chore of keeping
> mapping superproject branches to submodule branches in my head.

At my former day-job we wrote our own "git submodule" in our build system before gitlink was available in the core, let alone git-submodule was a Porcelain command.

Many developers who were new to Git found having a sea of 11 Git repositories+working directories in a single build area difficult to manage. They quickly found the detached HEAD feature in a submodule to be a really handy way to know if they made changes there or not.

Most of our developers also modified __git_ps1() in their bash completion to use `git name-rev HEAD` to try and pick up a remote branch name when on a detached HEAD. This slowed down their bash prompts a little bit, but they found that "origin/foo" hint very valuable to let them know they should start a new branch before making changes.

So I'm just echoing what Benjamin said above, only we did it independently, and came to the same conclusion.

-- 
Shawn.