fix expansion of the Log keyword with rsync origins
Align our expansion of Log keywords with the behaviour of a real CVS server. With this, such keywords expand the same way over the pserver and rsync access methods.
This is the last change required to consistently ingest CVS's own CVS repository over both pserver and rsync. Otherwise we get commit hash mis-matches due to differently expanded Log keywords.
Migrated from D6745 (view on Phabricator)