improves notes about staging area

basics.html

@@ -509,19 +509,19 @@
           </section>
 
           <section id="internals-staging-area" data-markdown>
-            ## internals
-            ### the staging area
+            ## the staging area
 
             ![staging area](img/staging-area.svg)
 
             notes:
-            - can I have your attention, please?
-            - content can be in three stages
-            - we make changes, these are not yet known to git
-            - we prepare a commit by **successively** adding changes to the
-            staging area
-            - we commit this **set of changes**
-            - a commit **should be a logical unit** of changes
+            - **don't demo here! that's done during next slide, this one is
+              about the concept of the staging area**
+            - **call for attention, this is important**
+            - in a local git repository, content can be in three stages
+            - make local changes, these are **not yet** known to git
+            - **prepare** commit adding more and more **changes**
+            - **commit** this **set of changes**
+            - commit **should be a logical unit** of changes
           </section>
 
           <section id="cli-git-files" data-markdown>