Say, we have a number of people working on some kind of collaborative effort (such as a research paper or a software project) that is committed into a shared repository. However, a certain subset of these people are also conspiring against the rest of the people involved so as to deny them authorship. The motivations could be, for example, taking credit for other people's work, denying others the recognition or money they deserved as contributors, and so on.
The threat model here involves institutions without a fixed control structure and without an effective higher authority located in-house which could resolve such a dispute, as is often the case for hobby projects worked upon by friends, and in certain situations, research papers. (Just to be clear, we do have a judiciary where legal disputes can be brought.)
Timestamps and authorship information in the repository itself does not provide any valid proof, since the conspirators can just as easily recreate another version of the repository which would show that the commits have been made just by them.
Is there a protocol, which, if followed by every person committing to the repository, would allow the victims to prove their authorship should a dispute arise?