Otherwise, a call to, for example, nix-prefetch-git, in a nix-shell --pure or
nix-build phase would result in an error such as:
Switched to a new branch 'fetchgit'
removing `.git'...
/nix/store/7qvjji7kbd033nsyxlpiiiam61a44yz9-nix-prefetch-git/bin/.nix-prefetch-git-wrapped: line 374: nix-hash: command not found