What steps will reproduce the problem?
(1) Upload a Gerrit patch for one branch (e.g. ToT)
(2) Run a tryjob with a -g argument referencing that patch and a -b argument referencing a different branch (e.g. some firmware branch)

What is the expected result?

The tryjob fails with a clear error, e.g. "CL:XXX is not compatible with branch Y". Bonus points if this check is done during the execution of the cros tryjob command and not 30 minutes later on the server. Extra bonus points if the tryjob just runs correctly instead when the patch can be cleanly cherry-picked across branches.

What happens instead?

https://logs.chromium.org/v/?s=chromeos%2Fbb%2Fchromiumos.tryserver%2Ffirmware%2F228%2F%2B%2Frecipes%2Fsteps%2FPatchChanges%2F0%2Fstdout

This tryjob was started with:

 cros tryjob -g 957711 -b firmware-oak-8438.B hana-firmware

The most clear indication about what the problem is is the enigmatic line:

ChangeNotInManifest: CL:957711 could not be found in the repo manifest.