The "/tree" page:
Show the files using a tree-view.  If the ci= query parameter is present
then show only the files for the check-in identified.  If ci= is omitted,
then show the union of files over all check-ins.
The type=tree query parameter is required or else the /dir format is used.
Query parameters:
- type=tree
 - Required to prevent use of /dir format
 - name=PATH
 - Directory to display. Optional
 - ci=LABEL
 - Show only files in this check-in. Optional.
 - re=REGEXP
 - Show only files matching REGEXP. Optional.
 - expand
 - Begin with the tree fully expanded.
 - nofiles
 - Show directories (folders) only. Omit files.
 - sort
 - 0: by filename, 1: by mtime, 2: by size