Using {#} removes argument

[Jay Hacker]

$ parallel echo ::: a b c
a
b
c

$ parallel echo {#} ::: a b c
1
2
3

I'm not sure this is a problem (I prefer it this way), but it should
probably be documented.  It's the normal behavior for all of the other
{} substitutions, but {#} is kind of different: it doesn't have
anything to do with the input.  This makes it perhaps a bit unexpected
that it takes away the input.

Actually the docs don't explicitly say that using {} disables the
normal append-input-as-args behavior; this might be good to mention.
Also that all of the {...} substitutions disable input-append, not
just {}.