The attached patch adds a regression test for this bug, as well as a
couple other basic functionality tests for insert-directory. This does
not test the other unfixed cases still in ls-lisp.el and tramp-sh.el,
but I thought it prudent to get these tests in before trying to apply
them in other libraries.

Along those lines, I also attempted to skip the test when ls-lisp
would be used during files-tests.el, which I predict might happen when
building on Windows?

I sent in my copyright assignment, but I think it's still being
finalized.

Thank you!