Add space-padding to missing tracks dialog

[jams2]

Hi all,
during a long session organising my library with Beets, I found readability was not great after a while, this might help.
Not sure how to write tests for this, happy to be pointed in the right direction, and happy to look at other dialogs if this is helpful.

[sampsyo]

This looks really great; thanks for looking into it!

Just for the sake of thoroughly considering the alternatives, how about this idea: instead of moving over the right-hand column by a fixed amount, we could move it over by the length of the longest track name. This is sort of like how we already lay out the “arrow” (->) in the metadata change display. This could make things more compact—although I’m not sure that’s better or worse than what you already have. I’d be interested in your thoughts, though!

[jams2]

Yep, that might be a better option. I had a soft-limit of 80 characters in the back of my mind, but that's pretty arbitrary. I'll look into it.

[jams2]

@sampsyo made your suggested change, looks good I think!

[sampsyo]

Nice!! That looks fantastic. Great work; and thanks for the insight that this could be made better! ✨

[jams2]

Happy to help out.