Well, I actually think yet another macro would be too much work no ? Good
text can fix your points I believe, e.g.:
http://wiki.ros.org/Installation/Angstrom
And for instructions that don't change much (like OSX I guess), well, it's
the guy that usually writes the page that will fix it no ? One page with
ROS-distro sections, or a bunch of includes (like what I did): his call no ?