make mercurial look in more places for config files. now it searches <install dir>/etc/mercurial, /etc/mercurial, and user hgrc. this allows site-wide configuration to be shared over automounted nfs partition, instead of chenging on every system. option of having local configuration on every system remains. old code for searching /etc/mercurial/hgrc.d never worked, this code is tested and works.

fix the cat command - improve localrepo.walk when passed a node - make the differents walk commands in commands.py accept a node - change commands.cat to walk over a revision - add a test

abort when merging two heads and repository has local changes

Merge http://sh0n.net/jeffpc/repos/hg-gitweb/