serve-branches doesn't work with file-system paths, causes error 404s

[edam]

Running serve-branches with a filesystem path (and not using --allow-writes), like this:

  $ ./serve-branches ~/bzr

will cause loggerhead not to be able to access the specified path and it will always respond with error 404 over http.

This is because:

1. in loggerhead/main.py, when --allow-writes is not present, "readonly+" is pre-pended to the path to the bzr repos.

    E.g., "/home/edam/bzr" becomes "readonly+/home/edam/bzr"

2. in loggerhead/apps/transport.py, get_transport_for_thread(), which calls bzrlib's get_transport(), is called on the path. When the path has not specified protocol, this treats the "readonly+" as part of the path.

    E.g., "readonly+/home/edam/bzr" becomes "file:///home/edam/www/ed.am/bzr/readonly%2B/home/edam/bzr/"

The result is obviously wrong.

The solution to this seems to be to always specify a full path *and protocol* to the bzr repos. So, in the above example, the server can successfully be run like this:

  $ ./serve-branches file:///home/edam/bzr