narrowspec: replace one recursion-avoidance hack with another When updating the working copy narrowspec, we call context.walk() in order to find which files to update the working copy with. context.walk() calls repo.narrowmatch(). In order to avoid infinite recursion in this case, we have a hack that assigns the new values for repo.narrowpats and repo._narrowmatch. However, doing that of course breaks future invalidation of those properties (they're @storecache'd). Let's instead avoid the infinite recursion by setting a flag on the repo instance when we're updating the working copy. Differential Revision: https://phab.mercurial-scm.org/D6468