histedit: add forceother constraint For the future 'base' action in histedit we need a verification constraint which will not allow using this action with changes that are currently edited.

histedit: make verification configurable Before we can add a 'base' action to histedit need to change verification so that action can specify which steps of verification should run for it. Also it's everything we need for the exec and stop actions implementation. I thought about baking verification into each histedit action (so each of them is responsible for verifying its constraints) but it felt wrong because: - every action would need to know its context (eg. the list of all other actions) - a lot of duplicated work will be added - each action will iterate through all others - the steps of the verification would need to be extracted and named anyway in order to be reused The verifyrules function grows too big now. I plan to refator it in one of the next series.

paper: show current revision on file log page Most of the pages in paper (and coal) style show the current revision and its branch, tags and bookmarks. Let's also show all this on file log page.

merge.applyupdates: extend action queues with ones returned from mergestate These queues will always be empty at the moment -- we're going to fill them up in upcoming patches.