log: bypass file scan part of fastpath when no files This avoids loading dirstate parents, looking up p1 rev, and loading p1 manifest to match against an empty matcher.

cmdutil: use context instead of lookup

scmutil: use context instead of lookup

localrepo: lookup now goes through context

context: use rev for changelog lookup Faster when we're doing numeric scanning

context: internalize lookup logic This allows us to avoid doing rev->node->rev lookups on silly instances like "0", which end up caching the whole nodemap.

revlog: allow retrieving contents by revision number

revlog: add hasnode helper method