I have something quite disturbing wrt to paths and case: starting 'emacs -Q' from the same directory,
I can get 3 different values for default-directory:
This is with a mingw64 shell, after doing 'cd /d/Source/emacs/build-master' and running 'emacs -Q'
This is with a mingw64 shell, after doing 'cd /d/source/emacs/build-master' and running 'emacs -Q'
This is with a cmd shell, after doing 'd:' and 'cd d:/Source/emacs/build-master'
I have not (yet) traced the origin but such paths should be canonicalized to a single form.
Currently, tests occasionnaly fail because of these different forms.