comint history question

[unfrostedpoptart]

Hi.

I use shell-mode for almost all my command shells. I don't understand
why the comint history (e.g. comint-previous-matching-input) doesn't
keep one and two-character commands. I frequently mess myself up by
hitting ctl-up ret to rerun the last command and instead run a
different command because the last one was only two characters (e.g.
ls).

I'm actually running xemacs, but I don't that's an issue here.  How to
I get comint history to use all commands?

Thanks,

 David