When using working-directory, the changes files list does not provide a list of files relative to the working directory. It provides the list relative to the parent directory.
I am facing the same issue. trying to do a build for subfolder but the docker image should be built only on the changes on pyproject.toml in those folders not in general.
When using working-directory, the changes files list does not provide a list of files relative to the working directory. It provides the list relative to the parent directory.