comint-completion-addsuffix

comint-completion-addsuffix is a variable defined in `comint.el'.
Its value is

t

Documentation:
If non-nil, add ` ' to file names.
It can either be a string FILESUFFIX or a cons (DIRSUFFIX . FILESUFFIX)
where DIRSUFFIX is ignored and FILESUFFIX is a string added on unambiguous
or exact completion.
This mirrors the optional behavior of tcsh.

You can customize this variable.