no package-install if source is available locally

  This commit updates all places where packages are automatically
  installed using ELPA to first check if the package is available from a
  local source directory (i.e., under the src/ directory).  This makes
  it possible for users to override the ELPA versions of packages with
  local versions from source.  E.g., with this change I'm able to run my
  own fork of magit and starter-kit-misc.org will not install magit from
  ELPA.

starter-kit-misc.org

@@ -12,7 +12,7 @@ Determine whether required packages are installed. If not, use ELPA to
 install them. Other dependencies are provided by Emacs 24.
 #+begin_src emacs-lisp
   (dolist (package '(magit))
-    (unless (package-installed-p package)
+    (unless (or (starter-kit-loadable-p package) (package-installed-p package))
       (package-install package)))
 #+end_src
 

starter-kit-python.org

@@ -13,7 +13,7 @@ Determine whether required packages are installed. If not, use ELPA to
 install them.
 #+begin_src emacs-lisp
   (dolist (package '(python-mode ipython))
-    (unless (package-installed-p package)
+    (unless (or (starter-kit-loadable-p package) (package-installed-p package))
       (package-install package)))
 #+end_src
 

starter-kit-ruby.org

@@ -25,7 +25,7 @@ Support for the [[http://www.ruby-lang.org/en/][Ruby]] dynamic, open-source prog
 ** Yaml mode
 #+begin_src emacs-lisp
   (dolist (package '(yaml-mode))
-    (unless (package-installed-p package)
+    (unless (or (starter-kit-loadable-p package) (package-installed-p package))
       (package-install package)))
   (require 'yaml-mode)
   (add-to-list 'auto-mode-alist '("\\.ya?ml$" . yaml-mode))

starter-kit.org

@@ -305,7 +305,7 @@ interested in the actual code implementing the starter kit.
     (unless package-archive-contents
       (package-refresh-contents))
     (dolist (package starter-kit-packages)
-      (unless (package-installed-p package)
+      (unless (or (starter-kit-loadable-p package) (package-installed-p package))
         (package-install package)))
   #+end_src