+ a colon. For example, "master:docs/readme.mkd". If the value begins
+ with a colon, i.e. ":docs/readme.rst", the default branch of the
+ repository will be used. Sharing any file will expose that entire
+ directory tree to the "/about/PATH" endpoints, so be sure that there
+ are no non-public files located in the same directory as the readme
+ file. Default value: <readme>.