extdatasource: use revsymbol() for converting to node It's unclear what we want to support here. Perhaps it should just be nodeids? It doesn't make much sense to share revnums between repos, and bookmarks are probably too unstable. I used scmutil.revsymbol() to preserve the current behavior. We can change later if we want to. Differential Revision: https://phab.mercurial-scm.org/D3088