On the 'move-tracking-2' branch: Add assertions.
On the 'move-tracking-2' branch: Add assertions.

* subversion/libsvn_delta/branch.c
  (branch_validate_element): Also validate that a subbranch root element is
    not the branch root element. Simplify an existing assertion.
  (svn_branch_update_subbranch_root_element): Don't call
    branch_validate_element() here, as it is called inside branch_map_set().
  (svn_branch_add_new_branch): Assert that a branch does not already
    exist at this location.

git-svn-id: 486ec3464084f62cfe8608152673c827b947faa2@1676748 13f79535-47bb-0310-9956-ffa450edef68

YueLinHo/Subversion,YueLinHo/Subversion,YueLinHo/Subversion,YueLinHo/Subversion,YueLinHo/Subversion,YueLinHo/Subversion,YueLinHo/Subversion,YueLinHo/Subversion