Re: gnulib bootstrap and git submodules

[Jim Meyering]

Eric Blake wrote:
> git 1.6.4 learned 'git submodule add --reference dir' as a means to make
> initializing git submodules use (MUCH) less bandwidth and disk space by
> borrowing references from an existing on-disk repository, rather than
> cloning from scratch.  I would like to modify the bootstrap script to
> honor $GNULIB_SRCDIR, if set, as the argument to the --reference
> directory, to take advantage of this git feature.  Keep in mind that if
> someone sets GNULIB_SRCDIR, it should be to a master repository that does
> not get rewound, to avoid issues with the client repositories ever
> depending on references that might go stale during garbage collection in
> the reference repository (but with gnulib's linear development model, that
> is probably not too much of a concern).  Any objections?

Good idea.
I will use it, and end up saving at least 5 copies worth.

> Additionally, the m4 bootstrap script (m4 does not use the gnulib
> bootstrap script) is able to perform the same operation even with older
> git-submodule that does not support the --reference action, by breaking
> things down into multiple steps and using git-clone --reference instead.
> Is that worth incorporating into my proposed patch for gnulib's bootstrap,
> or should we just assume that git 1.6.4 or newer is widespread enough to
> not be worth the hassle?

I'd prefer to assume git 1.6.4 to keep things simpler, at least until
someone comes up with a compelling reason to add code to support older git.