Merge pull request symfony#815 from mdpatrick/bin_vendors_lock

Added reference to bin/vendors lock

Author: weaverryan

cookbook/workflow/new_project_git.rst

@@ -118,6 +118,10 @@ script to ensure that all of the needed vendor libraries are downloaded.
     by updating them to the version specified in ``deps`` and recording it
     into the ``deps.lock`` file.
 
+    Additionally, if you would simply like to update the ``deps.lock`` file
+    to what you already have installed, then you can simply run ``php bin/vendors lock``
+    to store the appropriate git SHA identifiers in the deps.lock file.
+
 Vendors and Submodules
 ~~~~~~~~~~~~~~~~~~~~~~