implement stable melpa fetcher

core/core-configuration-layer.el

@@ -186,7 +186,8 @@ LAYER has to be installed for this method to work properly."
 (defvar configuration-layer--elpa-archives
   '(("melpa" . "melpa.org/packages/")
     ("org"   . "orgmode.org/elpa/")
-    ("gnu"   . "elpa.gnu.org/packages/"))
+    ("gnu"   . "elpa.gnu.org/packages/")
+    ("melpa-stable" . "stable.melpa.org/packages/"))
   "List of ELPA archives required by Spacemacs.")
 
 (defvar configuration-layer-no-layer nil
@@ -493,6 +494,11 @@ If TOGGLEP is nil then `:toggle' parameter is ignored."
          (protected (when (listp pkg) (plist-get (cdr pkg) :protected)))
          (copyp (not (null obj)))
          (obj (if obj obj (cfgl-package name-str :name name-sym))))
+    (when (and (listp location)
+               (eq (car location) 'recipe)
+               (eq (plist-get (cdr location) :fetcher) 'stable))
+      (configuration-layer/pin-stable-package name-sym)
+      (setq location nil))
     (when location (oset obj :location location))
     (when min-version (oset obj :min-version (version-to-list min-version)))
     (when step (oset obj :step step))
@@ -1866,7 +1872,10 @@ FILE-TO-LOAD is an explicit file to load after the installation."
             (1+ configuration-layer-error-count))
     (setq configuration-layer-error-count 1)))
 
+(defun configuration-layer/pin-stable-package (package)
+  "Pin PACKAGE to melpa-stable."
+  (push `(,package . "melpa-stable") package-pinned-packages))
+
 (provide 'core-configuration-layer)
 
 ;;; core-configuration-layer.el ends here
-