Explain the ✂ symbol

docs/intro/narrative.rst

@@ -68,6 +68,16 @@ right of each code snippet.
 Clicking on that icon will copy all relevant lines from the code snippet,
 and will drop all comments and the ``$`` automatically.
 
+Whenever you see a ✂ symbol, command output has been shortened for easier readability.
+In the example below, the commit :term:`shasum` has been shortened and marked with ``✂SHA1``.
+
+.. code-block:: bash
+
+   $ git log --reverse
+   commit 8df130bb✂SHA1
+   Author: Elena Piscopia <[email protected]>
+   Date:   Tue Jun 18 16:13:00 2019 +0000
+
 The book is split into different parts. The upcoming chapters
 are the *Basics* that intend to show you the core DataLad functionality
 and challenge you to use it. If you want to learn how to use DataLad, it is