Prevent space after directories in tcsh completion

Prevent space after directories in tcsh completion

If git-completion.bash returns a single directory as a completion,
tcsh will automatically add a space after it, which is not what the
user wants.

This commit prevents tcsh from doing this.

Also, a check is added to make sure the tcsh version used is recent
enough to allow completion to work as expected.

Signed-off-by: Marc Khouzam <redacted>
Signed-off-by: Junio C Hamano <redacted>