Describe the bug

I'm using git-crypt to manage my config, and since this nixpkgs commit I can't build it anymore using flakes:

It fails when trying to load some of the secrets of the repo, because they're still encrypted (it looks like the flake build re-clones my local repo elsewhere, ending up in a state where nothing is decrypted yet)

Steps To Reproduce

• Use git-crypt to encrypt some secrets in a repo.
• Use fileContents to load one of these secrets in a Nix string
• Run nix build
• get error about the file's content not being representable as a nix string, because it's binary garbage since it's still encrypted

Expected behavior

building a flake that uses git-crypt should still work?

Additional context

I've bisected the regression up to PR #4922