Does fetchFromGithub ignore `rev` when a derivation with equivalent `sha256` is present?

From my own experiences, yes. But I don’t know why. I expect a change in any field in fetchFromGithub (and similar) would yield a different derivation hash. I’ve had multiple occasions where I need a build to crash to see what must be fixed when bumping a version, so I usually just replace a random character in rev to force the rebuild. Not very elegant. Is there a more convenient way?