Add "git" and "git-log-script" helper scripts.

The "git" script is just shorthand: "git xyz <args>" will just execute
"git-xyz-script <args>", which is useful for people used to the CVS
naming convention. So "git log" will run the new git-log-script, which
is just a wrapper around the new pretty-printing git-rev-list.

Cheesy.

git-log-script

@@ -0,0 +1,2 @@
+#!/bin/sh
+git-rev-list --pretty HEAD | LESS=-S ${PAGER:-less}