narrow: don't resurrect old commits when narrowing (don't strip obsmarkers) If you have an old obsolescence-chain of commits that has been pruned and you narrow your repo so that some of those commits get stripped (because they affected the removed paths), then we would currently resurrect the commit that came before (along the obsmarker chain) the last stripped commit. That happens by the usual rules for obsmarker-stripping. However, it's quite surprising when it happens when you narrow your repo. This patch makes narrowing not strip obsmarkers. Differential Revision: https://phab.mercurial-scm.org/D5364