A ticket needs to track of MPs in addition to source packages. This includes the MP itself, the revision of the linked branch, the merge target and the merge target revision.
A ticket may contain multiple branches which could target different trunks (i.e. 3 MPs target lp:foo, 2 MPs target lp:bar/utopic, etc.)
The MPs will be submitted or updated through the UI. The revision and trunk branch info will come later via the branch source builder (it will take a 'snapshot' of the branch info when the build starts). The publisher will consume this information to determine if the contents have changed.
The branch source builder can get the set of MPs from the fullticket API. It will need an API to specify the remaining details per MP. Something like:
curl --dump-header - -H "Content-Type: application/json" -X PATCH --data '{"MP": "https://code.launchpad.net/~user/project-name/branch-name/+merge/123456", "revision": "123", "target": "lp:project-name", "target_revision": "120"}' http://localhost:8000/api/v1/updatemp/1/
The publisher can get the MPs and revisions from the fullticket API.
BSB subornate charm was disabled (removed from j-d configs) temporarily because it was consuming a lot of time in deployments for no benefit.
It has to be re-enabled (re-designed really) as part of this task.