I'd like to use a Choice Parameter to select the Mercurial URL to clone from. Something like:

repository=foo

Mercurial URL: http://server/${repository}

but the variable doesn't get substituted:

abort: HTTP Error 404: Not Found
ERROR: Failed to clone http://server/${repository}

Searching the bug database I found JENKINS-9686 which is kind of related. A quick look at the code tells me this is just not implemented but supporting it seems trivial.