Comment 6 for bug 1372286

another observation as an addon to my previous post (I'd liked to edit it but unfortunately I can't)

less /tmpX<TAB> # gives "less /tmpX/" on the same line
type lv # gives "lv is /usr/bin/lv"
lv /tmpX<TAB> # gives "lv /tmpX " with a trailing space

So it is supposedly not the alias but some other mechanism.
Maybe it is a changed default for "unknown" commands.

P.S.
ls /etc/bash_completion.d # on my ubuntu 14.04.1 LTS gives
 apt-file axi-cache debconf gem1.9.1 grub initramfs-tools insserv pon ufw upstart

cat /etc/bash_completion # gives
. /usr/share/bash-completion/bash_completion

ll /usr/share/bash-completion/bash_completion # gives
-rw-r--r-- 1 root root 67659 Apr 7 2014 /usr/share/bash-completion/bash_completion