The posix 'sh' specification defines vi-mode editing quite tightly.
The netbsd libedit code (used by sh to do this) was missing several
features, there were also minor errors in others.
Compare netbsd sh to the definition available from:
http://www.opengroup.org/onlinepubs/007904975/utilities/sh.html
In particular the following were not supported:
U - undo all changes to line
| - goto column
Y - yank to end of line
y - yank
# - comment out current line
@ - take input from shell alias [1]
G - goto numbered line in history buffer
v - edit history line with vi
_ - append word from last input line
. - redo last command
Other minor changes have also been made.
[1] This needs the shell to define an appropriate routine to
return the text of the alias. There is no requirement that
such a function exist.
