For bulk copying, `rsync` is used in test code, which is rather fast and
capable of saving needless write operations. The downside is that tests
fail when the tool is missing, which is the case with most minimal Linux
setups (e.g. containers or even Gnome installations of Debian).
Provide an alternative way for sufficiently fast copying by means of
`find -exec cp`. Measured total test time penalty is less than 0.5%.
Downside of needless write operations remains in case of fallback.
Removed the copy/paste code, moved it into a reusable function that can
be called from the `local_setup` function as needed. Also simplified the
handling of the $HOME variable since @rico-chet provided a better way of
doing this.
Can't use the official v0.4.0 release, since our tests rely on a change
that was made after the release of v0.4.0.
This code currently uses an unversioned commit of the bats-core repo, we
will switch to a supported version once it has been released, e.g.
v0.4.1.
