package-archive-priorities doc addition

* lisp/emacs-lisp/package.el (package-archive-priorities):
Document that negative priorities will lead to packages not being
updated (bug#28897).

diff --git a/lisp/emacs-lisp/package.el b/lisp/emacs-lisp/package.el
index 43a9aa7f710adb13361094c0e243f860f2a6b407..9a350aadaca55e36875ae97f06bd16c4320e5e1e 100644 (file)
--- a/lisp/emacs-lisp/package.el
+++ b/lisp/emacs-lisp/package.el
@@ -252,7 +252,9 @@ number from the archive with the highest priority is
 selected.  When higher versions are available from archives with
 lower priorities, the user has to select those manually.
 
-Archives not in this list have the priority 0.
+Archives not in this list have the priority 0, as have packages
+that are already installed.  If you use negative priorities for
+the archives, they will not be upgraded automatically.
 
 See also `package-menu-hide-low-priority'."
   :type '(alist :key-type (string :tag "Archive name")