[Bug-readline] Readline 7.0 and history-search-backward/forward

[Rahul Kumar]

I'm not sure if this is a bug, but after upgrading to Ubuntu 18.04
(which uses Readline 7.0) from an earlier version (using Readline 6.0),
the behavior of history-search-backward/forward in Bash seems to be
a bit different.  I have the following lines in my ~/.inputrc to cyle
through Bash's command line history:

  "\eOA": history-search-backward
  "\eOB": history-search-forward
  "\e[A": history-search-backward
  "\e[B": history-search-forward

Now, if I start with an empty ~/.bash_history and type in a two-word
command like

  $ echo helloworld

and try to complete the arguments to echo the next time

  $ echo <arrow-up>

the command gets completed twice:

  $ echo helloworld
  echo helloworld

Which on pressing the return key runs the command twice.  I figured out
that this can be fixed by making the first line of ~/.bash_history an
empty blank line.  Though I'm not 100% that this is a bug, I thought
I should report this.

-Rahul