contrib/plan9/proto

rust-files: check for empty manifests caused by narrow

Explanations inline

lib	- sys sys
	mercurial	- sys sys
		hgrc.d	- sys sys
			9diff.rc	- sys sys
			factotum.rc	- sys sys
rc	- sys sys
	bin	- sys sys
		9diff	- sys sys
		hg	- sys sys
sys	- sys sys
	lib	- sys sys
		python	- sys sys
			lib	- sys sys
				python2.5	- sys sys
					site-packages	- sys sys
						hgext	- sys sys
							+	- sys sys
						mercurial	- sys sys
							+	- sys sys
						mercurial-VERSION-py2.5.egg-info	- sys sys
	src	- sys sys
		cmd	- sys sys
			hg	- sys sys
				+	- sys sys