add note about fetching tags

HACKING.rst

@@ -59,6 +59,19 @@ Clone the repository using::
 
     git clone https://github.com/saltstack/salt
 
+.. note:: tags
+
+    Just cloning the repository is enough to work with Salt and make
+    contributions. However, you must fetch additional tags into your clone to
+    have Salt report the correct version for itself. To do this you must first
+    add the git repository as an upstream source.::
+
+        git remote add upstream http://github.com/saltstack/salt
+
+    Fetching tags is done with the git 'fetch' utility::
+
+        git fetch --tags upstream
+
 Create a new `virtualenv`_::
 
     virtualenv /path/to/your/virtualenv