hg-ssh: normalize the drive of the current working directory on windows
For some reason os.getcwd() can return either `c:` or `C:`. We normalize this to
`C:` and the like. This fix `test-ssh-bundle1.t` on windows.
Differential Revision: https://phab.mercurial-scm.org/D11042
$ hg init
$ touch unknown
$ touch a
$ hg add a
$ hg ci -m "1"
$ touch b
$ hg add b
$ hg ci -m "2"
Should show unknown
$ hg status
? unknown
$ hg revert -r 0 --all
removing b
Should show unknown and b removed
$ hg status
R b
? unknown
Should show a and unknown
$ ls -A
.hg
a
unknown