ci: Add pipeline change detection

[phlax]

Signed-off-by: Ryan Northey ryan@synca.io

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part of #23758

[alyssawilk]

hah I was about to ask if it was easier for you to pick this up than suggest all the fixes. Thanks so much for tackling it! LMK when this is ready as I'd love to get something in this week

[phlax]

i have not added any actual exclusions to this PR - just the framework for detecting changes - as when we add any exclusions we need to think carefully about how it will run on main or other release branches and on tagged commits/releases

im inclined to not exclude anything when a PR lands - this does risk PRs passing and then failing when they land - but i would rather that than commits passing and then releases not passing and i think we need to ensure every change is tested somewhere

[phlax]

testing PR is #24204

[phlax]

this is probably gtg altho we may need to iterate - testing is hard because the PR introduces change itself

[alyssawilk]

I'd be inclined to land with at least one CI we think is affected (i.e. https://github.com/envoyproxy/envoy/pull/24204/files) as I'm not sure landing this as-is is going to tell us anything. WDYT?

[phlax]

WDYT?

adding a change here is probably not going to help as the PR contains change itself

i think land this and then run the test PR a couple of times, and then clarify what should/not be excluded

[phlax]

adding a change here is probably not going to help as the PR contains change itself

hmm, actually thinking about it - yep i see - we need at least one thing to be excluded to test - ill add ...

[alyssawilk]

yeah I'll also say now we have this (or almost) I am so excited to say not run all the Envoy tests for docs only changes. This is going to be pretty awesome :-D

[phlax]

k - ive added a condition which hopefully will only run coverage all checks iff either:

• commit is postsubmit (on any branch)
• the PR is neither docs-only nor mobile-only

should work

[alyssawilk]

Let's see how it goes :-)