manifestv2: implement slow readdelta() without revdiff For manifest v2, revlog.revdiff() usually does not provide enough information to produce a manifest. As a simple workaround, implement readdelta() by reading both the old and the new manifest and use manifest.diff() to find the difference. This is several times slower than the current readdelta() for v1 manifests, but there seems to be no other simple option, and this is still much faster than returning the full manifest (at least for verify).