Ensure author & committer before asking for commit message.

It's better to find out you need to fix your author and
committer information before you enter a long commit message.

Signed-off-by: Sean Estabrooks <seanlkml@sympatico.ca>
Signed-off-by: Junio C Hamano <junkio@cox.net>

git-commit.sh

@@ -640,6 +640,8 @@ case "$no_edit" in
 		exit 1
 		;;
 	esac
+	git-var GIT_AUTHOR_IDENT > /dev/null  || die
+	git-var GIT_COMMITTER_IDENT > /dev/null  || die
 	${VISUAL:-${EDITOR:-vi}} "$GIT_DIR/COMMIT_EDITMSG"
 	;;
 esac