largefiles: use more reasonable locking for update

largefiles: full debugdirstate functionality for largefiles - just reusing the original command with a mockup repo. This makes it possible to see dates in the lfdirstate and gives less code duplication.

largefiles: make cat on standins do something cat of a standin would silently fail. The use of standins is mostly an implementation detail, but it is already a bit leaking. Being able to see the content of standins might be convenient for debugging.

largefiles: remove confusing handling of .bad return value - it is void

largefiles: fix profile of unused largefilesdirstate._ignore

largefiles: import whole modules instead of importing parts of them Be more friendly to demandimport.

largefiles: update should only create a .orig backup of a largefile once A .orig of a standin after the update do that a .orig of the actual largefile is created. The .orig standin was however never removed again and the largefile .orig was thus overwritten again and again. The fix: remove the standin .orig when it is used.

merge: let manifestmerge emit 'keep' actions when keeping wd version Such a 'keep' action will later be the preferred (non)action when there is multiple ancestors. It is thus very convenient to have it explicitly. The extra actions will only be emitted in the case where the local file has changed since the ancestor but the other hasn't. That is the symmetrical operation to a 'get' action. This will create more action tuples that not really serve a purpose. The number of actions will however have the number of changed files as upper bound and it should thus not increase the memory/cpu use significantly.

merge: pass merge ancestor to calculateupdates as a list The list will so far always have one element.

merge: move ancestor selection tweaking from manifestmerge to update function - passing it through calculateupdates. This will make sure manifestmerge actually use the ancestor it is given.