Redirect "hg clone" (BB-1450)

When you delete a repository and configure a redirection, then it would be nice if this would make {{

{hg clone OLD-URL}

}} work. Mercurial knows how to follow standard 301 Moved Permanently headers.

Perhaps you want to check that the redirection is done to a repository internally on Bitbucket so that you know that it makes sense to redirect. In any case, the current message is not very informative for users:
{{

{\\ % hg clone https://bitbucket.org/mg/commitsigs\\ destination directory: commitsigs\\ abort: The OPTIONS response did not include the requested\\ activity-collection-set; this often means that the URL is\\ not WebDAV-enabled (SVN_ERR_RA_DAV_OPTIONS_REQ_FAILED)\\ }}

}