Tarmac fails to resolve pre-req branches when they've already been merged

[Stuart Colville]

If you have Branch A which is a pre-req of branch B. If branch A has already been merged into trunk when tarmac looks to merge branch B it rejects it saying it can't find a merge proposal for branch A.

Here's an example error message:

"No proposals found for merge of lp:~muffinresearch/ubuntuone-servers/ie-streaming-fixups-2 into lp:ubuntuone-servers."

[dobey (dobey)]

This is actually a bug in Launchpad, it seems. Sometimes it will fail to give the branch in the requested list of proposals. This seems to happen regardless of the prerequisite's merge status, but does seem to occur more often when it has been merged.

[Stuart Colville (muffinresearch)]

Would there be a way to work around this by examining branch B (in the example above) looking directly at the pre-req and determining that it is or isn't merged into the target branch?

Ideallly I'd love to be able to mark all proposed branches in a pipeline as approved and let tarmac deal with it (it should skip where the pre-req isn't merged rather than provide a comment complaining about it and changing the approval status).