On the 'move-tracking-2' branch: Operate on the given base revision.

* subversion/svnmover/svnmover.c
  (fetch_repos_info): Take a base revision and use it instead of always 'head'.
  (execute): Pass the base revision to fetch_repos_info().

git-svn-id: https://svn.apache.org/repos/asf/subversion/branches/move-tracking-2@1628144 13f79535-47bb-0310-9956-ffa450edef68