[m-dev.] git submodules

[Paul Bone]

Hi.

The Mercury programming langauge uses BDW GC.  We've made a few changes to
the GC and so we build it in the Mercury tree, libatomic_ops also.

I'm about to upgrade Mercury to use BDWGC 7.4.2 (from 7.2) and this is an
opportunity to change the way we track the GC's changes as it's the first
upgrade since we started using git (from CVS).

I'm considering using git submodules to import the GC's sources into
Mercury's build tree:

    mercury/
    mercury/boehm_gc
    mercury/boehm_gc/libatomic_ops

And if I import the gc's sources this way it would be convenient for the GC
to import libatomic_ops sources in a similar way.  I don't know if this is
useful or desirable for anyone else but I thought I'd ask because it will
change what I do next.

I've submitted a pull request that adds libatomic_opts as a submodule.
After checking out the collector's sources you can issue "git submodule
update --init" to import libatomic_ops.  Git will look for the
libatomic_opts repository at location relative to the "origin" repository of
../libatomic_opts.git  (I think, I'm still learning how to use submodules.)

https://github.com/ivmai/bdwgc/pull/61

Thanks.


-- 
Paul Bone