dispatch: parse and apply -R early
This allows us to use extensions specified in .hg/hgrc. Unfortunately,
this requires us to parse that file twice, but performance impact on
the version command appears to be less than 1%.
adding a
1 files updated, 0 files merged, 0 files removed, 0 files unresolved
adding b
pushing to ../a
abort: could not lock repository ../a: Permission denied