RFC: remove support for ranges as a commit option

[MasterDuke17]

I don’t think it (e.g., 1218.12..HEAD) has ever been used in the wild so it’s just an extra code path to maintain and test.

[AlexDaniel]

I agree. Personally I did use it a few times (it was something like 2018.10..HEAD when there were not many commits after the release, also I remember doing something like 2018.10~100..2018.10), but nowadays I'd much rather use Whateverable as a library and run it on my own computer (gist). Feel free to remove the feature and the corresponding tests.