Need to pass --name to nix-prefetch-url if the attribute is present

[jwiegley]

[terlar]

Is this related to a definition like this not working?

      src = fetchgit {
        url = https://git.savannah.gnu.org/git/emacs.git;
        rev = "c418c85617babbe7b63730fefb71e2c87a0141af";
        sha256 = "1m374vaq5zaylds7g049vx1j8d67hv69pmdnsrnaypmj83gqf46x";
      };

If I run the command on this I will get:

      src = fetchgit {
        url = https://git.savannah.gnu.org/git/emacs.git;
        rev = "refs/heads/fetchgit";
        sha256 = "0sjjj9z1dhilhpc8pq4154czrb79z9cm044jvn75kxcjv6v5l2m5";
        # date = ;
      };

I got the same behavior with fetchFromGitHub if I was using a variable for repo.