Log Message:
Update to 2.2.1:

This is an unscheduled bugfix release to fix a signficant memory leak in hgweb.

    bookmarks: catch the proper exception for missing revisions
    help: add reference to template help (issue3413)
    help: added description for the web.collapse setting
    largefiles: fix commit of both largefiles and non-largefiles (issue3354)
    parsers: fix refcount leak, simplify init of index (issue3417)