interactive: add doc() function

... that prints the welcoming message

port_stats/interactive.py

@@ -35,6 +35,8 @@ What's in the box:
   - dump
   - append_to
   - pager
+* other:
+  - doc(): print this message.
 
 You can also enjoy autocompletion with <TAB>.
 """
@@ -288,6 +290,10 @@ def stats(names=None, to=dump):
     to(reports.color_totals(BY_COLOR, names, total, summary=True))
 
 
+def doc(to=dump):
+    to(__doc__)
+
+
 def interactive_setup():
     # Bind ‘TAB’ to complete
     readline.parse_and_bind('tab:complete')
@@ -319,4 +325,4 @@ def interactive_setup():
 
 if __name__ == '__main__':
     interactive_setup()
-    print(__doc__)
+    doc()