To use astro(1) and scat(1) one has to create sky/here and download various catalogue files as detailed in sky/README. This change marks those files as ignored by git so they don't clutter its status messages.

- rewrite .gitignore to use git patterns - mv hg(1) to git(1) and rewrite - add lib/git/commit-msg.hook - add skeleton codereview script - update codereview(1) Change-Id: I061cd8e4de77ebbd6037a7c5d1582cd1d986f62f