emacs: add onChange script to run doom sync and add missing symbols font

programs/emacs/default.nix

@@ -1,14 +1,43 @@
-{ pkgs, ... }:
+{ pkgs, lib, ... }:
 
 {
-  programs.emacs = {
-    enable = true;
+  programs.emacs.enable = true;
 
-    home.packages = with pkgs; [
-      # Optional for DOOM
-      clang
-      coreutils
-      fd
-    ];
-  };
+  home.packages = with pkgs; [
+    # Optional for DOOM
+    clang
+    coreutils
+    fd
+
+    pandoc # For org-pandoc
+  ];
+
+  # Neatly place the configuration files for doom in their right place.
+  xdg.configFile."doom" =
+    let
+      # What DOOM needs to be able to install/sync.
+      packagesNeeded = with pkgs; [
+        git
+        emacs
+        ripgrep
+      ];
+    in
+    {
+      source = ./doom;
+      recursive = true;
+
+      onChange = # sh
+        ''
+          # Need to set this so DOOM can find all binaries.
+          export PATH="${lib.strings.concatMapStrings (x: x + "/bin:") packagesNeeded}$PATH"
+
+          if [ ! -d "$HOME/.emacs.d" ]; then
+            git clone https://github.com/hlissner/doom-emacs $HOME/.emacs.d
+            $HOME/.emacs.d/bin/doom install
+          else
+            # Needed to apply the configuration changes.
+            $HOME/.emacs.d/bin/doom sync
+          fi
+        '';
+    };
 }