Copilot setup steps are very expensive

[agocke]

The steps in copilot-setup-steps are very expensive and are often not necessary. For instance, it includes building clr+libs and installing dependencies. For docs and workflow changes, this is not necessary.

I also see copilot running these steps multiple times on the same PR -- the setup is not necessarily saved in between runs.

I think we should consider removing all these steps and let copilot determine what it needs to run.

[agocke]

cc @jkotas @stephentoub who have some experience with using copilot for PRs

[agocke]

#120817 is an example where the instructions cause multiple hours of building when no building should be necessary at all.

[stephentoub]

IIRC, we did this on advice from the copilot coding agent folks because the setup steps activity doesn't count against the time limit (nor the firewall) whereas copilot initializing the build does. That was back in May, though... it's possible things have changed since then.

[agocke]

Do you know if it’s supposed to save anything between runs? I was surprised that every comment i made caused it to restart from scratch

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[ViktorHofer]

Great issue, fully agree. I.e. since recently, building and packaging libraries doesn't require upfront steps anymore aside from restoring the .NET SDK mentioned in global.json. Of course, for running the tests we still need the live runtime as we don't fallback to an LKG for that.