cros tryjob -h

Payloads:
  Options only used by payloads tryjobs.

  --version PASSTHROUGH
                        Specify the release version for payload regeneration.
                        Ex: 9799.0.0
  --channel PASSTHROUGH
                        Specify a channel for a payloads trybot. Can be
                        specified multiple times. No valid for non-payloads
                        configs.

branch_util:
  Options only used by branch-util tryjobs.

  --branch-name PASSTHROUGH
                        The branch to create or delete.
  --delete-branch       Delete the branch specified in --branch-name.
  --rename-to PASSTHROUGH
                        Rename a branch to the specified name.


All these PASSTHROUGH metavars should probably be given more illumintating names.