If the target directory as a file named X and a package has a
directory named X, or vice-versa, then it is impossible for Stow
to stow that entry X from the package, even if --adopt is supplied.
However we were previously only handling the former case, and not the
latter, and the test for the former was actually broken. So fix
stow_contents() to handle both cases correctly, fix the broken test,
and add a new test for the latter case.
34421ba5cf