narrow: detect if narrowspec was changed in a different share With this commit, `hg share` should be usable with narrow repos. Design explained on https://www.mercurial-scm.org/wiki/NarrowSharePlan I was running into cache invalidation problems when updating the narrowspec. After spending a day trying to figure out a good solution, I resorted to just assigning repo.narrowpats and repo._narrowmatch after invalidating them. Differential Revision: https://phab.mercurial-scm.org/D5278