[check-libraries] Detect library changes on PR without LIBPATCH bump

[taurus-forever]

Enhancement Proposal

Hi,

We are running check-libraries on PRs to make sure our charms are using the latest shared libraries.
The approach with green/red labels works perfectly: example.

What is missing is a human protection to inform author about forgotten LIBPATCH bump on the shared library change: example.

What about to set red label: Libraries: bump LIBPATCH if author changes shared library and forget to bump it?
At the moment the action simply prints notice and sets green label Libraries: OK:

Library charms.mongodb.v0.helpers has local changes, cannot be updated.
Library charms.mongodb.v0.mongodb_backups has local changes, cannot be updated.
Library charms.mongodb.v0.mongodb_vm_legacy_provider has local changes, cannot be updated.

We have tried to use option fail-build, but it didn't fail on locally changed library.
Is it a broken option or it was designed for something else? Tnx!

[taurus-forever]

Just for the history, the option fail-build fails the build if updates are available on charmhub, e.g.:

Library charms.operator_libs_linux.v1.snap updated to version 1.8.
Library charms.operator_libs_linux.v1.systemd updated to version 1.2.

The option fail-build does not react on locally modified libraries at all. It is not well documented.