In preparation for hotcopy progress reporting, inline the logic related to
the 'db/current' update.  As a consequence, we can now get rid of the in-out
semantics for the parameter denoting the destination's youngest revision.
From now on, it is immutable and always represents the youngest revision of
the destination at the point we started a hotcopy.  This is simpler and also
allows us to entirely drop two related helper functions.

* subversion/libsvn_fs_fs/hotcopy.c
  (hotcopy_update_current, hotcopy_update_current_old): Remove, now inline.
  (hotcopy_revisions): Make the 'dst_youngest' argument immutable instead of
    treating it as an in-out parameter.  Inline the hotcopy_update_current()
    calls and tweak the corresponding comments.
  (hotcopy_body): Make the 'dst_youngest' immutable for the whole hotcopy
    operation.  Its only usage happened during the part when we truncate the
    destination's rep-cache.db file.  Switch to using the source youngest
    revision as a threshold, because it does not really matter at this point
    -- we are done with copying the revisions and we did not error out, so
    the youngest revisions must be equal.  Finally, update the 'db/current'
    contents directly instead of calling the hotcopy_update_current() or
    hotcopy_update_current_old() functions.


git-svn-id: https://svn.apache.org/repos/asf/subversion/trunk@1612810 13f79535-47bb-0310-9956-ffa450edef68