Subject: bug#25870: give an example to show what lines join -a and -v are talking about

From: 積丹尼 Dan Jacobson <[email-masked]>
Date: Mon, 27 Feb 2017 18:26:11 +0800

I can't really tell, but it seems at the beginning there still lacks the
most basic "Hi kids, here is the 'join' command. It takes one file with
contents ... and and another file with contents ... and outputs ..."
before you get into any more niceties.