git-crypt won't work if git and git-crypt are not in PATH. This surfaced
after dbb8958. Test like this:
```
PATH= $(nix-build --no-out-link '<nixpkgs>' --attr git-crypt)/bin/git-crypt unlock
```
git-crypt won't work if git and git-crypt are not in PATH. This surfaced
after dbb8958. Test like this:
```
PATH= $(nix-build --no-out-link '<nixpkgs>' --attr git-crypt)/bin/git-crypt unlock
```