`fetchFromGitHub`, such as `hash` or `fetchSubmodules`.

## `dhall-to-nixpkgs` {#ssec-dhall-dhall-to-nixpkgs}

You can use the `dhall-to-nixpkgs` command-line utility to automate
packaging Dhall code.  For example:

```ShellSession
$ nix-shell -p haskellPackages.dhall-nixpkgs nix-prefetch-git
[nix-shell]$ dhall-to-nixpkgs github https://github.com/Gabriella439/dhall-semver.git
{ buildDhallGitHubPackage, Prelude }:
  buildDhallGitHubPackage {
    name = "dhall-semver";
    githubBase = "github.com";
    owner = "Gabriella439";
    repo = "dhall-semver";
    rev = "2d44ae605302ce5dc6c657a1216887fbb96392a4";
    fetchSubmodules = false;
    hash = "sha256-n0nQtswVapWi/x7or0O3MEYmAkt/a1uvlOtnje6GGnk=";
    directory = "";
    file = "package.dhall";
    source = false;
    document = false;
    dependencies = [ (Prelude.overridePackage { file = "package.dhall"; }) ];
    }
```

:::{.note}
`nix-prefetch-git` is added to the `nix-shell -p` invocation above, because it has to be in `$PATH` for `dhall-to-nixpkgs` to work.
:::

The utility takes care of automatically detecting remote imports and converting
them to package dependencies.  You can also use the utility on local
Dhall directories, too:

```ShellSession
$ dhall-to-nixpkgs directory ~/proj/dhall-semver
{ buildDhallDirectoryPackage, Prelude }:
  buildDhallDirectoryPackage {
    name = "proj";
    src = ~/proj/dhall-semver;
    file = "package.dhall";
    source = false;
    document = false;
    dependencies = [ (Prelude.overridePackage { file = "package.dhall"; }) ];
    }
```

### Remote imports as fixed-output derivations {#ssec-dhall-remote-imports-as-fod}

`dhall-to-nixpkgs` has the ability to fetch and build remote imports as
fixed-output derivations by using their Dhall integrity check. This is
sometimes easier than manually packaging all remote imports.

This can be used like the following:

```ShellSession
$ dhall-to-nixpkgs directory --fixed-output-derivations ~/proj/dhall-semver
{ buildDhallDirectoryPackage, buildDhallUrl }:
  buildDhallDirectoryPackage {
    name = "proj";
    src = ~/proj/dhall-semver;
    file = "package.dhall";
    source = false;
    document = false;
    dependencies = [
      (buildDhallUrl {
        url = "https://prelude.dhall-lang.org/v17.0.0/package.dhall";
        hash = "sha256-ENs8kZwl6QRoM9+Jeo/+JwHcOQ+giT2VjDQwUkvlpD4=";
        dhallHash = "sha256:10db3c919c25e9046833df897a8ffe2701dc390fa0893d958c3430524be5a43e";
        })
      ];
    }
```

Here, `dhall-semver`'s `Prelude` dependency is fetched and built with the
`buildDhallUrl` helper function, instead of being passed in as a function
argument.

## Overriding dependency versions {#ssec-dhall-overriding-dependency-versions}