This allows disabling a repository by pinning it to 'never',
which is internally translated to a value of -32768 (or whatever
the minimum of short is).
This overrides any other pin for that repository. It can be used
to make sure certain sources are never used; for example, in
To prevent semantic changes to existing files, we substitute
min + 1 for every pin-priority: <min>. This is a temporary
solution, as we are waiting for an ABI break.
To add pins with that value, the special Pin-Priority
"never" may be used for now. It's unclear if that will
persist, or if the interface will change eventually.