plugin: only catch ".*/D1234" patterns in URL snarfer

plugin: make differential snarfing actually work

plugin: use custom joiners for hghelp and changelog replies Using just one message instead of multiple for each line means less flood, so Limnoria does it by default. But the default joiner ("a, b, and c") is not very suitable for lines that refer to just one thing.

plugin: add more repos

plugin: snarf differential revisions and URLs

plugin: add a basic differential parser

plugin: describe the plugin

This is where your commit messages goes. For example: remove needless comment

plugin: move repo paths to config, finally add tests for changelog command

plugin: strip individual lines in changelog, and not skip empty lines Empty lines are still possible if (e.g. user is empty for null rev).