emacs-packages: Add easy wrapper script to update elpa

pkgs/applications/editors/emacs-modes/elpa-packages.nix

@@ -4,11 +4,9 @@
 
 To update the list of packages from MELPA,
 
-1. Clone https://github.com/ttuegel/emacs2nix.
+1. Run `./update-elpa`.
-2. Run `./elpa-packages.sh` from emacs2nix.
+2. Check for evaluation errors: `nix-instantiate ../../../.. -A emacsPackagesNg.elpaPackages`.
-3. Copy the new `elpa-generated.nix` file into Nixpkgs.
+3. `git commit -m "elpa-packages $(date -Idate) -- elpa-generated.nix"`
-4. Check for evaluation errors: `nix-instantiate ./. -A emacsPackagesNg.elpaPackages`.
-5. `git add pkgs/applications/editors/emacs-modes/elpa-generated.nix && git commit -m "elpa-packages $(date -Idate)"`
 
 */
 

pkgs/applications/editors/emacs-modes/emacs2nix.nix

@@ -0,0 +1,23 @@
+let
+  pkgs = import ../../../.. { };
+
+  src = pkgs.fetchgit {
+    url = "https://github.com/ttuegel/emacs2nix.git";
+    fetchSubmodules = true;
+    rev = "752fe1bd891425cb7a4a53cd7b98c194c1fe4518";
+    sha256 = "0asfdswh8sbnapbqhbz539zzxmv72f1iviha95iys34sgnd5k1nk";
+  };
+
+in pkgs.mkShell {
+
+  buildInputs = [
+    pkgs.bash
+  ];
+
+  EMACS2NIX = "${src}";
+
+  shellHook = ''
+    export PATH=$PATH:${src}
+  '';
+
+}

pkgs/applications/editors/emacs-modes/update-elpa

@@ -0,0 +1,4 @@
+#! /usr/bin/env nix-shell
+#! nix-shell --show-trace ./emacs2nix.nix -i bash
+
+exec elpa-packages.sh --names $EMACS2NIX/names.nix -o elpa-generated.nix