sheldon: add option to enable completion script

modules/programs/sheldon.nix

@@ -25,6 +25,18 @@ in {
       description = "";
       example = literalExpression "";
     };
+
+    enableZshCompletions = mkEnableOption "Zsh completions" // {
+      default = false;
+    };
+
+    enableBashCompletions = mkEnableOption "Bash completions" // {
+      default = false;
+    };
+
+    enableFishCompletions = mkEnableOption "Fish completions" // {
+      default = false;
+    };
   };
 
   config = mkIf cfg.enable {
@@ -36,10 +48,26 @@ in {
 
     programs.bash.initExtra = mkIf (cfg.settings != { }) ''
       eval "$(sheldon source)"
+    '' + mkIf cfg.enableBashCompletions ''
+      if [[ $TERM != "dumb" ]]; then
+         eval "$(${cmd} completions --shell=bash)"
+      fi
     '';
 
     programs.zsh.initExtra = mkIf (cfg.settings != { }) ''
       eval "$(sheldon source)"
+    '' + mkIf cfg.enableZshCompletions ''
+      if [[ $TERM != "dumb" ]]; then
+         eval "$(${cmd} completions --shell=zsh)"
+      fi
+    '';
+
+    programs.fish.interactiveShellInit = mkIf (cfg.settings != { }) ''
+      eval "$(sheldon source)"
+    '' + mkIf cfg.enableFishCompletions ''
+      if test "$TERM" != "dumb"
+         eval "$(${cmd} completions --shell=fish)"
+      end
     '';
   };
 }