I’m not sure if I’m your reading your point correctly, but fundamentally I agree and I’m massively annoyed by these kinds of problems.
(WIP)(RFC) A new nixpkgs frontend for language infrastructures - #2 by deliciouslytyped is intended to address this kind of structure.
However, a much simpler thing to do at least in this case - if a simple rec set is acceptable - is to make the self attr take an argument and pass gitBase as a parameter - if I’m following correctly.
I see two issues here; one is that let expressions are horrible for overridability, the other is whether what is consuming your inputs is parametrized over it’s scope (bad for overriding), or over explicit arguments (good for overriding). I use “horrible” to emphasize my strong feelings towards this, but I’m always open to being convinced otherwise.