Shared PR docs workflow: Be nicer during the BASE build

[felixfontein]

Avoid that errors in the PR target branch fail the docs build.

For example in ansible-collections/community.general#4881 the docs build fails because while the PR fixes the issues, the docs build is never run with these fixes.

[briantist]

This is a good catch, thank you. I'm trying to think over any scenarios where this would not be what we want, but I don't think that'd be the case. The only one I could think of is if it causes the diff between the base and pr to show changes that are not actually due to the PR itself.

Another thing I'm wondering then, is if the PR does NOT fix the errors already in BASE, won't think then make the PR fail? I suppose that's not different than what would happen already though... one is kind of forced to fix doc changes soon after implementing these actions for them to be useful.

So I guess, this change doesn't make anything worse in any scenario? Would appreciate you checking my assumptions!

[felixfontein]

Another thing I'm wondering then, is if the PR does NOT fix the errors already in BASE, won't think then make the PR fail?

Yes, but:

I suppose that's not different than what would happen already though... one is kind of forced to fix doc changes soon after implementing these actions for them to be useful.

Exactly. Except if you change the settings for the shared workflow to be lenient and not fail on errors, then it will pass despite errors.

So I guess, this change doesn't make anything worse in any scenario? Would appreciate you checking my assumptions!

I think so. At least I didn't mangage to think of a scenario where it would cause a problem that wasn't already around before.

[felixfontein]

@briantist thanks a lot for reviewing this! I'm going to test this in a few minutes by fixing some bugs in module docs in c.g ;-)