narrow: consider both local and remote matchers in narrowchangegroup The existing code that picked one or the other seemed very suspicious. This patch makes us intersect the local matcher with the matcher from the remote, which seems better. It fixes one test case and makes another one that used to crash no longer crash, but instead silently succeed with a push that's lossy, so that remains to be fixed. The real reason for doing this now is that I'm going to move narrowrepo.narrowmatch() onto localrepo and then it will always be defined, which would otherwise break this code. Differential Revision: https://phab.mercurial-scm.org/D2490

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