pre-commit: switch to git-var to check if username and e-mail are set

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.

pre-commit

@@ -41,14 +41,13 @@ Use the commands
 to introduce yourself to Git before committing.'
 
 # Ensure name and email are available.
-git config --get user.name > /dev/null &&
-git config --get user.email > /dev/null ||
+git var GIT_AUTHOR_IDENT > /dev/null ||
 die 'Identity not configured!' "$advice"
 
 # Validate the name and email.
-git config --get user.name | grep ' ' > /dev/null ||
+git var GIT_AUTHOR_IDENT | cut -d "<" -f1 | sed 's,\s$,,' | grep ' '  > /dev/null ||
 die 'Set user.name to your Real Name (with a space), not a userid.' "$advice"
-git config --get user.email | grep '^[^@]*@[^@]*$' > /dev/null ||
+git var GIT_AUTHOR_IDENT | cut -d ">" -f1 | cut -d "<" -f2 | grep '^[^@]*@[^@]*$' > /dev/null ||
 die 'Set user.email to an email address (userid@validdomain.com).' "$advice"
 
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