A kind of FAQ for libreadline on Debian GNU/{Linux,Hurd}
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0. symlinked directory completion behavior

Starting with readline-4.2a, completion on symlinks that point
to directories does not append the slash. To restore the behaviour
found in readline-4.2, add to /etc/inputrc or ~/.inputrc:

set mark-symlinked-directories on

1. re-enable the paren matching feature in readline-4.1

Add to /etc/inputrc or ~/.inputrc:

set blink-matching-paren on

2. key bindings for ESC

Consider the following .inputrc:

set editing-mode vi

keymap vi
"\M-[D": backward-char
"\M-[C": forward-char
"\M-[A": previous-history
"\M-[B": next-history

And, just to be certain, set -o reports that vi is on.

However, ESC k does not send me to the previous line.

I'm guessing that this is a conflict between bash's concept of a meta
keymap and its concept of vi's command-mode character -- which is to
say that its data structures don't properly reflect its implementation.

Note that if I remove the meta prefix, leaving lines like:
"[A": previous-history

That vi command mode keys work fine, and I can use the arrow keys in vi
mode, *provided I'm already in command mode already*. In other words,
bash is doing something wrong here such that it doesn't see the escape
character at the beginning of the key sequence even when in vi insert mode.

Comment from the upstream author: "This guy destroyed the key binding for
ESC, which effectively disabled vi command mode. It's not as simple as he
paints it to be -- the binding for ESC in the vi insertion keymap *must*
be a function because of the other things needed when switching
from insert mode to command mode.

If he wants to change something in vi's command mode, he needs
to use `set keymap vi-command' and enter key bindings without
the \M- prefix (as he discovered)."