Merge branch 'js/mingw-default-ident'

The logic to select the default user name and e-mail on Windows has
been improved.

* js/mingw-default-ident:
mingw: use domain information for default email
getpwuid(mingw): provide a better default for the user name
getpwuid(mingw): initialize the structure only once

diff --cc compat/mingw.c
Simple merge

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