Enhance commit view compare functionality
Created by: umpox
Originally from https://github.com/sourcegraph/sourcegraph/issues/22677
The other place it would be helpful to have the compare functionality is when viewing a commit. Users would like to select a given revision from a dropdown to compare to while in this view: https://sourcegraph.com/github.com/sourcegraph/sourcegraph/-/commit/85073d2fa79f0a106948494a0a84ae7c2c859a6a?visible=3
Common request and most recently called out by: