There's three general categories of unsolicited changes one might make: 1. The PR is a bug fix or feature that's critical for you, but you don't actually need

There's three general categories of unsolicited changes one might make: 1. The PR is a bug fix or feature that's critical for you, but you don't actually need upstream to merge it to use the fix yourself. 2. The PR is something quick and easy to do and if it doesn't get merged that's just no big deal. 3. The PR is a large amount of work that's entirely wasted if it doesn't get merged. For the first two, I see no reason to ask first. The third you generally should.