Version Control With Subversion Source

* subversion/svnlook/main.c
(cmd_table): Update usage message for 'tree' subcommand.
(do_tree): Add 'path' argument.
(subcommand_tree): Get optional path from the context baton, and
pass it to do_tree().

* doc/book/book/ch08.xml
Document the changes to 'svnlook tree'.