Firstly, the robot Mark speaks of already exists, it is called the Patch
Queue Manager, or PQM. There is a load of work being done on it right
now to make it much better though.
Secondly, I work on a project that uses PQM, and I like it. It is no
substitute for code review, where taste is exercised, but it does mean
that you can have confidence in your trunk.
Yes, you can get this with a human gatekeeper, but with thorough code
review the merging in to trunk can be done by a machine, so why not let
(No, PQM can't resolve merge conflicts, so you have to provide a branch that
will merge cleanly, usually by merging trunk first)