dirname() emulation has been added, as Msys2 lacks it.
* js/dirname-basename:
mingw: avoid linking to the C library's isalpha()
t0060: loosen overly strict expectations
t0060: verify that basename() and dirname() work as expected
compat/basename.c: provide a dirname() compatibility function
compat/basename: make basename() conform to POSIX
Refactor skipping DOS drive prefixes