Make 'svn resolve' print a warning when no useful option can be offered for a tree conflict, and point users at 'svn help resolve'.
Make 'svn resolve' print a warning when no useful option can be offered
for a tree conflict, and point users at 'svn help resolve'.

* subversion/svn/conflict-callbacks.c
  (build_tree_conflict_options): New output param which indicates whether
   any useful resolution options exist.
  (handle_tree_conflict): Print a message if no useful options exist. 


git-svn-id: f8a4e5e023278da1e04e203c7fe051e3c4285d88@1771799 13f79535-47bb-0310-9956-ffa450edef68

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