subrepo: add test for Windows relative-ish path with drive letter
Matt Harbison pointed out that Windows had some weird path syntax.
Fortunately it's rejected appropriately by pathauditor, so we're safe.
Let's test the behavior as we have a special handling for Windows drive
letters.
This patch includes a basic example. Maybe we'll need to extend the test
case further, but writing such tests on Linux isn't easy.
#require docutils gettext
$ $TESTDIR/check-gendoc da
checking for parse errors