Is your feature request related to a problem? Please describe.
I just added coverage combining within GitHub Actions for pymodbus and the coverage is lower than I wildly guessed. My first thought was 'am I collecting all the files I meant to?'

Describe the solution you'd like
I thought it would be helpful for coverage combine to output the files it processes via --verbose or some other more specific option.

Describe alternatives you've considered
I first thought about adding an ls -la coverage_reports/ to check the contents of the directory I passed to coverage combine, but that doesn't say what coverage actually combined.

Additional context
n/a