In git, apart from setting username and e-mail in .gitconfig it's also
possible to set username in /etc/passwd and set e-mail using EMAIL
environment variable.  The advantage of this method is that other
programs such as mutt or doxygen will pick up these settings up so
there is no need to set them separately in each program.  Current way
of checking if username and e-mail are set using git config results in
failure if they are set using this method.