[Dev] Trigger R.yml only only if there are changes to R.yml itself

[carlopi]

R.yml is otherwise triggered on every merge commit to main, seems noisy.

Idea is that it will trigger on PRs only when modifying itself (just to check consistency).

[Mytherin]

Thanks! Perhaps this could instead be triggered only in PRs and in nightly test runs, just like all other workflows?

[carlopi]

I think this is what should happen after this PR:
manual workflow trigger or repository trigger have this run (as before)
PR have this run if the R.yml file itself is changed, but otherwise default is no runs on PRs.

This last part can also go away, and saying it should run only on explicit triggers.

[Mytherin]

Shouldn't it also run on PRs? It seems the run was skipped for this PR

[carlopi]

I think that this PR gets evaluated against current main branch yml files, and they are all not triggered (R.yml file since it misses a section on pull_request and the other since they corrently have R.yml in their ignore list).

The idea would be that, after this is merged, any subsequent PR changing R.yml should trigger a workflow.