Allow implicit hooks/middleware to be disabled.

Fixes #1621.

leiningen-core/src/leiningen/core/project.clj

@@ -679,25 +679,27 @@
       (utils/error "cannot resolve" hook-name "hook"))))
 
 (defn load-hooks [project & [ignore-missing?]]
-  (doseq [hook-name (concat (plugin-hooks project) (:hooks project))]
-    ;; if hook-name is just a namespace assume hook fn is called activate
-    (let [hook-name (if (namespace hook-name)
-                      hook-name
-                      (symbol (name hook-name) "activate"))]
-      (load-hook hook-name)))
+  (when (and (:implicits project true) (:implicit-hooks project true))
+    (doseq [hook-name (concat (plugin-hooks project) (:hooks project))]
+      ;; if hook-name is just a namespace assume hook fn is called activate
+      (let [hook-name (if (namespace hook-name)
+                        hook-name
+                        (symbol (name hook-name) "activate"))]
+        (load-hook hook-name))))
   project)
 
 (defn apply-middleware
   ([project]
      (reduce apply-middleware project
-             (concat (plugin-middleware project)
-                     (:middleware project))))
+             (concat (plugin-middleware project) (:middleware project))))
   ([project middleware-name]
-     (if-let [middleware (utils/require-resolve middleware-name)]
-       (middleware project)
-       (do (when-not (:optional (meta middleware-name))
-             (utils/error "cannot resolve" middleware-name "middleware"))
-           project))))
+     (if (and (:implicits project true) (:implicit-middleware project true))
+       (if-let [middleware (utils/require-resolve middleware-name)]
+         (middleware project)
+         (do (when-not (:optional (meta middleware-name))
+               (utils/error "cannot resolve" middleware-name "middleware"))
+             project))
+       project)))
 
 (defn load-certificates
   "Load the SSL certificates specified by the project and register

sample.project.clj

@@ -165,10 +165,14 @@
              :repl {:plugins [[cider/cider-nrepl "0.7.1"]]}}
   ;; Load these namespaces from within Leiningen to pick up hooks from them.
   :hooks [leiningen.hooks.difftest]
-  ;; Apply these middleware functions from plugins to your project when it
-  ;; loads. Both hooks and middleware can be loaded implicitly by giving them a
-  ;; name matching a specific pattern as well as by listing them here.
+  ;; Apply these middleware functions from plugins to your project
+  ;; when it loads. Both hooks and middleware can be loaded implicitly
+  ;; or by being listed here.
   :middleware [lein-xml.plugin/middleware]
+  ;; These settings disable the implicit loading of middleware and
+  ;; hooks, respectively. You can disable both with :implicits false.
+  :implicit-middleware false
+  :implicit-hooks false
 
 ;;; Entry Point
   ;; The -main function in this namespace will be run at launch