check_dependent_project: retrigger once the PR description changes

[joao-paulo-parity]

Problem: paritytech/substrate#11148 was edited around 10 hours ago to no longer have a Cumulus companion

When that happened, however, the check-dependent-cumulus job was not run again.

Solution: Run the check-dependent-* jobs once the PR description changes. This is justified because edits to the PR's description might change its dependency chain, which matters for those jobs.

[mutantcornholio]

edits to the PR's description might change its dependency chain, which matters for those jobs.

Could you please elaborate on how this works?

[mutantcornholio]

Ah, okay, this is it, right?

[joao-paulo-parity]

it's referring to https://github.com/paritytech/pipeline-scripts#step-2-detect-all-dependents and subsequent steps

[mordamax]

@joao-paulo-parity if there were 2 companions, and vanity-service added 2 red (failed) statuses. Then you remove one companion, and we re-triggered check_dependent_project - will the other status be automatically removed or ignored somehow?
let me know if it's not clear :) not sure if I explained it enough

[joao-paulo-parity]

will the other status be automatically removed or ignored somehow?

Naively, all companion checks should be retried since companions might be related to each other. e.g. if a PR has both Polkadot and Cumulus companions and I remove the Polkadot one, the Cumulus check should be rerun because the Polkadot companion matters for it.

Optimally, we could have a smart script that can detect precisely which checks should be rerun based on what changed.

I don't think it's necessary for us to go for the optimized version right now since description edits shouldn't happen often; it's better to have something suboptimal in the short term rather than a complete lack of the feature.