Merge branch 'js/dirname-basename'

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

diff --cc compat/mingw.c
Simple merge

diff --cc compat/mingw.h
Simple merge

diff --cc git-compat-util.h
Simple merge

diff --cc path.c
Simple merge

diff --cc t/t0060-path-utils.sh
Simple merge