when a user runs `uplink share`, they get a bunch of results back,
given their configuration and existing access. one of the results
is a URL for in-browser sharing and hosting of the file.
first off, we want to make sure this URL is read only. we want to
avoid a situation where someone post this URL to some public
location, not realizing the access allows writes or deletes. if
a user really wants a URL with write/delete access, they can
construct it themselves.
secondly, we want to make sure the url is sharing a single path or
path prefix. having a url for multiple paths/path prefixes
indepedently again can be constructed of course, but should not
be the default behavior
Change-Id: I2ca2ebeea9f1c7d4bfbd7a437a32dc7a3b2a32cc
2bd9067ad5