[PATCH 2/2] allow running mklog as a filter

[Yury Gribov]

> +# XXX We should probably accept /dev/stdin or maybe magic autodetection of
> +# being supposed to get the patch from stdin.
> +#

Can we just set $diff to '-' if @ARGV is empty?

> +# In any case if we got the diff on stdin then write the ChangeLog to stdout.

Hm, this is breaks semantics: you only dump CL instead of CL+diff just 
because diff comes from stdin. Perhaps we could append contents of 
@diff_lines here?

> +if ($diff == "-") {

This will work but 'eq' is preferred way to compare strings.

-Y