On the fsx-1.10 branch: Eliminate most of the directory representation I/O during typical history traversal in FSX.
On the fsx-1.10 branch:
Eliminate most of the directory representation I/O during typical history
traversal in FSX.

To determine when & where the next relevant copy operation for a given path
happened, we need to inspect the copy-from info for all parent folders.
Prior to this patch, we would do that crawl for each reported revision.
Now we remember the next copy revision number and simply follow the path's
node revision chain until then.

* subversion/libsvn_fs_x/tree.c
  (fs_history_data_t): Add elements to remember the current noderev and
                       the next copy we found.
  (assemble_history): Store the new optional structure elements.

  (x_node_history): Update caller - new optional info not available.
  (history_prev): Add a quick code path for following a linear history.
                  Provide & reuse the "next copy" and "noderev" info.
  (fs_history_prev): Update caller - new optional info not available.

git-svn-id: 40002ad72c45bcd78a61b73a7ab5afec77c4e304@1680529 13f79535-47bb-0310-9956-ffa450edef68

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