Update git global configuration: always enable pager with diff command

.gitconfig

@@ -38,6 +38,9 @@
 [merge]
     tool = vimdiff
 
+[pager]
+    diff = true
+
 # git.debian.org specifics
 [url "git://anonscm.debian.org"]
     insteadOf = git://git.debian.org