dabbrev-expand behavior

[Dan Nicolaescu]

Hi,

Thanks for implementing dabbrev-expand in bash-4.0!

Unfortunately the behavior is not consistent with what dabbrev-expand
does in Emacs (and tcsh), so it will be quite confusing for users to
use.

Doing
# bind dabbrev-expand to it's canonical key:
$ bind '"\M-/":dabbrev-expand'

# Now run a few dummy commands to have stuff in history:
$ foa
$ fob
$ foo

# try using dabbrev-expand

$ fo
# now type M-/
# This will display:

$ fo  
foa   fob   foo
$ foa 

# Note that there's a space after "foa" and that all the possibilities
# are displayed.

This is not how dabbrev-expand normally works, it should not insert the
extra space, nor should it show all the possibilities.  
For one thing the extra space is confusing: say you also have "foaa" in
history, it's hard to guess that pressing M-/ again after seeing "foa "
will result in "foaa " being inserted.
When you have a lot of history, displaying the matches is not very
useful, there can be hundreds of them.  Just display a match and one can
quickly cycle through them by repeatedly pressing M-/.  The matches
should be in history order, the most recent ones should be first, the
older ones should follow.