| Function | is_valid_transition | Is it valid for this user to move this proposal to to next_state? |
| Class | TooManyRelatedBugs | A source branch has too many related bugs linked from commits. |
| Class | BranchMergeProposal | A relationship between a person and a branch. |
| Class | BranchMergeProposalGetter | See IBranchMergeProposalGetter. |