Action fails for packages with multiple manuals (due to a warning)

[stertooy]

If a package has multiple manuals, AutoDoc or GAPDoc will produce the following warning:
#I WARNING: Package contains multiple books, only using the first one
which causes this action to fail.

We could just filter those out like the "Label(s) may have changed" warning, but I think in the long run we should seriously consider this:

A different approach would be to add an option to the action that accepts a list of warnings to ignore.

Then, upon a CI fail, the user can verify themselves that the document built is in fact correct and ignore the warning in future CI jobs.

Originally posted by @Joseph-Edwards in BNasmith/alco/#24

In particular, I noticed that GAP's make_doc script filters out warnings about overfull hboxes, which is likely to be of interest for package manuals as well.

[fingolfin]

I guess even better would be to actually build all manuals. Alas, that's an issue for AutoDoc resp. the affected package's makedoc.g file.

But for us here, the solution would indeed be to add a way to specify "filters" (regex?) for filtering out certain warnings. We could even suggest some "standard filters" for certain kinds of warnings (ideally also with a note explaining what that warning is about, and why perhaps you should fix it instead of ignoring it ;-) )

[fingolfin]

To be clear: the "multiple books" message is issued by AutoDoc which currently doesn't support multiple books. See gap-packages/AutoDoc#151

So I'd say this is not an issue with this action, but rather with AutoDoc.

However in the issue description, other kinds of warnings are also discussed. So perhaps this issue should be renamed?