fix "cibtool trigger", and Request::commit — radicle-ci-broker

cibtool trigger created a “ref changed” event without a base commit. This meant that the rest of the CI broker couldn’t construct a list of commits since the base commit, which meant it could not create a Request::Trigger message to the CI adapter. This meant that cibtool trigger was useless. Fix that by making sure the base commit is added: either the parent commit of the what is specified with --commit or that commit itself, if there is no parent commit.

Request::commit has always been fallible, but previously it has not returned a Result, and instead if anything went wrong, it panicked. Panics are not good, so change the method to return a Result instead. That’s a breaking change: callers will now have to handle the result.

         let name =
             RefString::try_from(name.clone()).map_err(|e| CibToolError::RefString(name, e))?;
         let event = BrokerEvent::new(&rid, &name, &oid, None);
         let base = self.lookup_commit(rid, &format!("{oid}^")).unwrap_or(oid);
         let event = BrokerEvent::new(&rid, &name, &oid, Some(base));
         let db = args.open_db()?;
         let id = db.push_queued_event(event)?;

         before: Oid,
         after: Oid,
     ) -> Result<PushEvent, MessageError> {
         let push_commits: Vec<Oid> = repo
         let mut push_commits: Vec<Oid> = repo
             .history(after)?
             .take_while(|c| if let Ok(c) = c { c.id != before } else { false })
             .map(|r| r.map(|c| c.id))
             .collect::<Result<Vec<Oid>, _>>()?;
         if push_commits.is_empty() {
             push_commits = vec![before];
         }
         Ok(PushEvent {
             pusher,
             before,

     /// Return the commit the event concerns. In other words, the
     /// commit that CI should run against.
     pub fn commit(&self) -> Oid {
     pub fn commit(&self) -> Result<Oid, MessageError> {
         match self {
             Self::Trigger {
                 common: _,

                 patch,
             } => {
                 if let Some(push) = push {
                     *push.commits.first().unwrap()
                     if let Some(oid) = push.commits.first() {
                         Ok(*oid)
                     } else {
                         Err(MessageError::NoCommits)
                     }
                 } else if let Some(patch) = patch {
                     *patch.patch.commits.first().unwrap()
                     if let Some(oid) = patch.patch.commits.first() {
                         Ok(*oid)
                     } else {
                         Err(MessageError::NoCommits)
                     }
                 } else {
                     panic!("neither push not panic: {self:#?}");
                     Err(MessageError::UnknownRequest)
                 }
             }
         }

     #[error("RequestBuilder has no event handler set")]
     NoEventHandler,
     /// Request message lacks commits to run CI on.
     #[error("unacceptable request message: lacks Git commits to run CI on")]
     NoCommits,
     /// Request message is neither a "push" nor a "patch"
     #[error("unacceptable request message: neither 'push' nor 'patch'")]
     UnknownRequest,
     /// Failed to serialize a request message as JSON. This should
     /// never happen and likely indicates a programming failure.
     #[error("failed to serialize a request into JSON to a file handle")]