Upgrade other repos than the current one by running git-annex upgrade
inside them, which avoids problems with upgrade code making assumptions
that the cwd will be inside the repo being upgraded.
In particular, this fixes a problem where upgrading a v7 repo to v8 caused
an ugly git error message.
I actually could not find a way to make Upgrade.V7 work properly
without changing directory to the remote. Once I got git ls-files to work,
the git cat-file failed because :path can only be used in the current git
repo.
This means it will still be a .git file when git-annex init runs. That's
ok, the repo probably contains no annexed objects yet, and even if it does,
git-annex init does not care if symlinks in the worktree don't point to the
objects.
I made init, at the end, run the conversion code. Not really necessary
because the next git-annex command could do it just as well. But, this
avoids commands that don't normally write to the repo needing to write to
it, which might avoid some problem or other, and seems worth avoiding
generally.
md5sum is part of busybox, so is probably available unless it were compiled
out. If md5sum (or cut for that matter) is not available, it will
still use the whole path to $base, otherwise hash it.
Of course it's possible for md5sum to be available sometimes and not others
on the same system; in such an event the locales would be built twice for
the same bundle. The cleanup code will delete both sets once that
version of the bundle is upgraded.
