descent3: init at 1.5.0-beta-unstable-2024-10-29

By default, Descent 3 will only look for game files in the current
working directory. In order to function properly, Descent 3 needs to
look for some of its files in the Nix store. This commit creates a
wrapper around the main Descent3 executable that automatically looks in
the correct path in the Nix store.

Hopefully, this wrapper will only exist temporarily. I have an
unfinished Descent 3 pull request that adds a DEFAULT_ADDITIONAL_DIRS
CMake option [1]. Once I can finish that pull request
(DescentDevelopers/Descent3#623 needs to get merged first), we’ll be
able to get rid of this wrapper and use DEFAULT_ADDITIONAL_DIRS instead.
Additionally, if DescentDevelopers/Descent3#628 gets merged first, then
that pull request will also probably make this wrapper unnecessary.

[1]: <DescentDevelopers/Descent3#471>

pkgs/by-name/de/descent3/package.nix

@@ -0,0 +1,60 @@
+{
+  descent3-unwrapped,
+  lib,
+  makeBinaryWrapper,
+  runCommand,
+}:
+
+runCommand "descent3-${descent3-unwrapped.version}"
+  {
+    pname = "descent3";
+    inherit (descent3-unwrapped) version;
+    nativeBuildInputs = [ makeBinaryWrapper ];
+    passthru.unwrapped = descent3-unwrapped;
+
+    meta = descent3-unwrapped.meta // {
+      # The code that produces the wrapper is in the Nixpkgs repo, and the
+      # Nixpkgs repo is MIT Licensed.
+      license = [ lib.licenses.mit ];
+      longDescription = ''
+        Playing Descent 3 using the Nix package manager is a little bit awkward
+        at the moment. This wrapper makes it slightly less awkward. Here’s how
+        you use this wrapper:
+
+        1. Install the `descent3` package, or start an ephemeral shell with the
+        `descent3` package.
+
+        2. Find the documentation folder for `descent3-unwrapped` by running this
+        command:
+
+            ```bash
+            nix-instantiate --eval --expr '(import <nixpkgs> { }).descent3-unwrapped + "/share/doc/Descent3"'
+            ```
+
+        3. Open `<descent3-unwrapped-doc-folder>/USAGE.md`.
+
+        4. Follow steps 1–6 of Descent 3’s usage instructions.
+
+        5. Change directory into the `D3-open-source` folder:
+
+          ```bash
+          cd <path-to-D3-open-source>
+          ```
+
+        6. Start Descent 3 by running this command:
+
+            ```bash
+            Descent3
+            ```
+      '';
+    };
+  }
+  ''
+    mkdir --parents "$out/bin"
+    descent3_unwrapped=${lib.strings.escapeShellArg descent3-unwrapped}
+    makeBinaryWrapper \
+      "$descent3_unwrapped/bin/Descent3" \
+      "$out/bin/Descent3" \
+      --append-flags -additionaldir \
+      --append-flags "$descent3_unwrapped/share"
+  ''