Add zsh completions

Signed-off-by: Nikolaos Karaolidis <nick@karaolidis.com>

hosts/common/configs/user/console/nix-develop/default.nix

@@ -2,12 +2,14 @@
   user ? throw "user argument is required",
   home ? throw "home argument is required",
 }:
-{ ... }:
+{ lib, inputs, ... }:
 {
   home-manager.users.${user}.programs.zsh = {
     shellAliases.nd = "nix-develop";
 
-    initExtra = ''
+    initExtra = let
+      devShells = lib.strings.concatStringsSep " " (lib.attrsets.mapAttrsToList (key: _: key) inputs.self.devShells);
+    in ''
       nix-develop() {
         if [ -z "$1" ]; then
           echo "Usage: nix-develop <shell>"
@@ -15,6 +17,13 @@
         fi
         nix develop self#"$1" -c "$SHELL"
       }
+
+      _nix-develop-completion() {
+        local shells=(${devShells})
+        compadd -- $shells
+      }
+
+      compdef _nix-develop-completion nix-develop
     '';
   };
 }