blackbox: log incoming changes via ui.log() Logs incoming changes to a repo to ui.log(). Includes the number of changes and the hashes of the heads after the new changes. Example log line: 2013/02/09 08:35:19 durham> 1 incoming changes - new heads: cb9a9f314b8b Currently the blackbox logs the unix user that is performing the push/pull. It would be nice to log the http authorized user as well so it works with hgweb, but that's outside the scope of this commit.