phases: return zero for no-op operations (issue4751) (BC) It is rather unhelpful to return 1 if there were no changes because the request matches the current state of phases. So we just undo that.

help: add config.troubleshooting section at the top

dispatch: don't stack trace on commands like `hg .log` This used to stack trace because it raised a util.Abort which wasn't handled in this block. We now handle it. Additionally, we error out earlier instead of plodding on and showing the "log" entry of the plain `hg help` output.