questions on tarballs and efficient bootstrapping

[Ted Zlatanov]

I have two related questions to speed up the EMBA builds:

First, from a raw git checkout, what's the best way to snapshot "only
the things that go into the builds and tests"? So for example I don't
need BUGS and I don't think I need ChangeLog*

make-dist doesn't do it, giving me various errors along the way (I tried
many options). This has to work from a branch, a tag, or any commit. I
could use `git-archive-file` or `git-archive` but wasn't sure if that
captures too much.

Second, how do I know when some changes should trigger a bootstrap? Most
changes don't require that, and the bootstrap and compilation phase are
pretty expensive. Ideally I would have a way to say "looking back,
what's the latest commit that required a bootstrap" because then I can
fetch the Docker image bootstrapped for that commit instead of building
a new one.

Thanks
Ted