Add option to include TOTAL line even if there's only one file

[lordjabez]

Is your feature request related to a problem? Please describe.
Currently the total line is skipped when there's only one file whose coverage was computed. This is annoying when using a regex to report on coverage from a CI/CD build log (e.g. in Gitlab) because one can't use the recommended regex.

Describe the solution you'd like
Either always print the TOTAL line, or add an option to force it even when there's only one file.

[nedbat]

This has been requested before (#732, #922). I think my mind has changed, and we can go ahead and add an option for this.

[lordjabez]

@nedbat I'd be happy to take a crack at coding it up. Do you have a preference on the option name? --always-show-total ? --show-total ? Something else?

[nedbat]

Thanks. I would name it --always-total. Don't forget the .coveragerc option.

[nedbat]

I hope this doesn't sound aggravating, but maybe the better path here is to just always output the total line, without an option.

[lordjabez]

Not aggravating at all, I'm more than happy to go with a simpler solution.

I'll submit a new PR (and make sure all the tests still pass).

[nedbat]

This is now released as part of coverage 5.4.