A branch on which to prototype a model of move-tracking and branching.

This experimental functionality is exposed through one stand-alone dev
tool 'tools/dev/svnmover' and through one undocumented environment
variable 'SVN_ELEMENT_MERGE' which hooks the code in to the 'svn merge'
command.

Status:

  This approach to move tracking is not currently being pursued. It is
  retained for historical reference.

Merge policy:

  Development branch -- periodic catch-up merges from trunk.

  The work on this branch may or may not eventually be wanted on trunk. It
  is not intended to be kept in a state where it could be merged to trunk.

See notes/move-tracking/README for further details of this work.