POST requests are blocked when running in --no-edit mode so using POST
prevents compare being available (see #1546).
Change the history view form to use "get" as the form method and change
the routing in app to accept get requests for both forms of compare. The
order of the compare routes is switched to make the more specific form
checked first to prevent all requests being handled by the less specific
form.
Peter Holloway
83abe62125