merge: check created file dirs for path conflicts only once (issue5716) In large repositories, updates involving the creation of many files check the same directories repeatedly in the wctx manifest. Move these checks out to a separate loop to avoid repeated checks hitting the manifest. Differential Revision: https://phab.mercurial-scm.org/D1226

{
    "conduit_uri": "https://phab.mercurial-scm.org/api",
    "repository.callsign": "HG",
    "arc.land.onto.default": "@",
    "base": "hg:.^"
}