"/approved-entries" lists in the RepositoryMirror are applicable only
to the path where they are originally made. However, when a path is
copied, the "/a-e" entries are copied too. They then inhibit proper
pruning. A symptom of this is that in main-cvsrepos,
partial-prune/permanent is included in T_ALL_INITIAL_FILES, though
this tag is not set on that file.
The fix is to purge /a-e entries when /mutable entries are purged,
when a revision is stabilized. This is sufficient, as revisions are
only mutable whilst being constructed, and the current revision will
never be copied from - hence with this modification, an /a-e entry
will never be copied.