The upstream luafilesystem tarball/version had a wayward/inconsistent
underscore in their more recent version tag. The played badly with
our package fetching machinery (due to recent changes?).
Upstream cleaned up their bit which required some touchups here.
- updated the url
- updated the version (digest)
- updated the format statement for the path to the rockspec.
See #2059 for background.
I'm unable to install `lmod` because lua-luafilesystem fails.
The luarocks install bits attempt to do a shallow clone of the luafilesystem
sources and the default git on my CentOS 7 test box (`git version 1.8.3.1`)
fails.
This adds a build dependency that ensures that a relatively modern git is
available.
