setup-user: 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.

Utilities/GitSetup/setup-user

@@ -20,12 +20,12 @@
 # Project configuration instructions: NONE
 
 for (( ; ; )); do
-	user_name=$(git config user.name || echo '') &&
-	user_email=$(git config user.email || echo '') &&
-	if test -n "$user_name" -a -n "$user_email"; then
+	ident="$(git var GIT_AUTHOR_IDENT 2>/dev/null | rev | cut -d' ' -f3- | rev)"
+
+	if test -n "$ident"; then
 		echo 'Your commits will record as Author:
 
-  '"$user_name <$user_email>"'
+  '"$ident"'
 ' &&
 		read -ep 'Is the author name and email address above correct? [Y/n] ' correct &&
 		if test "$correct" != "n" -a "$correct" != "N"; then