RE: Uninitialized submodules as symlinks

[David Turner <David.Turner@twosigma.com>]

> -----Original Message-----
> From: Duy Nguyen [mailto:pclouds@gmail.com]
> Sent: Monday, October 17, 2016 5:46 AM
> To: David Turner
> Cc: Stefan Beller; git@vger.kernel.org
> Subject: Re: Uninitialized submodules as symlinks
> 
> On Sat, Oct 8, 2016 at 2:59 AM, David Turner <David.Turner@twosigma.com>
> wrote:
> >
> >
> >> -----Original Message-----
> >> From: Stefan Beller [mailto:sbeller@google.com]
> >> Sent: Friday, October 07, 2016 2:56 PM
> >> To: David Turner
> >> Cc: git@vger.kernel.org
> >> Subject: Re: Uninitialized submodules as symlinks
> >>
> >> On Fri, Oct 7, 2016 at 11:17 AM, David Turner
> >> <David.Turner@twosigma.com>
> >> wrote:
> >> > Presently, uninitialized submodules are materialized in the working
> >> > tree as empty directories.
> >>
> >> Right, there has to be something, to hint at the user that creating a
> >> file with that path is probably not what they want.
> >>
> >> >  We would like to consider having them be symlinks.  Specifically,
> >> > we'd like them to be symlinks into a FUSE filesystem which
> >> > retrieves files on demand.
> >> >
> >> > We've actually already got a FUSE filesystem written, but we use a
> >> > different (semi-manual) means to connect it to the initialized
> submodules.
> >>
> >> So you currently do a
> >>
> >>     git submodule init <pathspec>
> >>     custom-submodule make-symlink <pathspec>
> >>
> >> ?
> >
> > We do something like
> >
> > For each initialized submodule: symlink it into the right place in
> > .../somedir For each uninitialized submodule: symlink from the FUSE
> > into the right place in .../somedir
> >
> > So .../somedir has the structure of the git main repo, but is all
> symlinks -- some into FUSE, some into the git repo.
> >
> > This means that when we initialize (or deinitialize) a submodule, we
> need to re-run the linking script.
> 
> Do .git files work? If .git files point to somewhere in fuse, I guess you
> still have file retrieval on demand. It depends on what files to retrieve
> I guess. If you want worktree files, not object database then .git files
> won't work because worktree remains in the same filesystem as the super
> repo.

Yes, we want worktree files (or even worktree files + built artifacts).