first some examples that look fine ...

these all output the same thing:
	realpath --relative-to=/usr /usr/bin
	realpath --relative-to=/usr/ /usr/bin
	realpath --relative-to=/usr /usr/bin/
	realpath --relative-to=/usr/ /usr/bin/
which is to say, they show:
	bin

as does these:
	realpath --relative-to=/usr/bin /usr
	realpath --relative-to=/usr/bin/ /usr
	realpath --relative-to=/usr/bin /usr/
	realpath --relative-to=/usr/bin/ /usr/
which is to say, they show:
	..

as does these:
	realpath --relative-to=/ /usr
	realpath --relative-to=/ /usr/
which is to say, they show:
	..

however, if the last argument is just the root path:
	realpath --relative-to=/usr /
	realpath --relative-to=/usr/ /
we end up with a trailing slash:
	../

for consistency, i don't think that should be the case

(reported by Ulrich Müller via https://bugs.gentoo.org/398339)
-mike