doc/Makefile: Don't show Makefile comments in output
The comments makes sense when editing Makefile, but not when watching its
output where it looks too much like error messages.
#!/bin/sh
hg init a
hg clone a b
cd a
echo '[paths]' >> .hg/hgrc
echo 'dupe = ../b' >> .hg/hgrc
hg in dupe | fgrep '../'
cd ..
hg -R a in dupe | fgrep '../'
true