* admin/notes/elpa: Update to match recent Gnu ELPA changes

admin/notes/elpa

@@ -5,17 +5,31 @@ repository named "elpa", hosted on Savannah.  To check it out:
 
   git clone git://git.sv.gnu.org/emacs/elpa
   cd elpa
-  git remote set-url --push origin git+ssh://git.sv.gnu.org/srv/git/emacs/elpa
-  [create task branch for edits, etc.]
+  make setup
 
-Changes to this branch propagate to elpa.gnu.org via a "deployment" script run
-daily.  This script (which is kept in elpa/admin/update-archive.sh) generates
-the content visible at https://elpa.gnu.org/packages.
+That leaves the elpa/packages directory empty; you must check out the
+ones you want.
 
-A new package is released as soon as the "version number" of that package is
-changed.  So you can use 'elpa' to work on a package without fear of releasing
-those changes prematurely.  And once the code is ready, just bump the
-version number to make a new release of the package.
+If you wish to check out all the packages into the packages directory,
+you can run the command:
+
+   make worktrees
+
+You can check out a specific package <pkgname> into the packages
+directory with:
+
+   make packages/<pkgname>
+
+
+Changes to this repository propagate to elpa.gnu.org via a
+"deployment" script run daily.  This script generates the content
+visible at https://elpa.gnu.org/packages.
+
+A new package is released as soon as the "version number" of that
+package is changed.  So you can use 'elpa' to work on a package
+without fear of releasing those changes prematurely.  And once the
+code is ready, just bump the version number to make a new release of
+the package.
 
 It is easy to use the elpa branch to deploy a "local" copy of the
 package archive.  For details, see the README file in the elpa branch.