Move to git as primary source repository. * Makefile.am (git-dist, git-release): Renamed and adjusted from ... (cvs-dist, cvs-release): ... these. (git-diff): New target, taken and adjusted from cvs-diff. * Makefile.in: Regenerate. * bootstrap: Adjust. * NEWS: Announce change. * doc/automake.texi (General Operation): cvs-dist is git-dist now. (Timeline): Mention change.