narrow: only wrap dirstate functions once, instead of per-reposetup chg will call reposetup multiple times, and we would end up double-wrapping (or worse) the dirstate functions; this can cause issues like OSError 'No such file or directory' during rebase operations, when we go to double-delete our narrowspec backup file. Differential Revision: https://phab.mercurial-scm.org/D3559