Clarify how "hide" and "unhide" commands work on directories.

svn path=/head/; revision=253252

sbin/devfs/devfs.8

@@ -25,7 +25,7 @@
 .\"
 .\" $FreeBSD$
 .\"
-.Dd April 21, 2013
+.Dd July 12, 2013
 .Dt DEVFS 8
 .Os
 .Sh NAME
@@ -190,6 +190,7 @@ Nodes may later be revived manually with
 or with the
 .Cm unhide
 action.
+Hiding a directory node effectively hides all of its child nodes.
 .It Cm include Ar ruleset
 Apply all the rules in ruleset number
 .Ar ruleset
@@ -213,6 +214,8 @@ which may be a user name
 or number.
 .It Cm unhide
 Unhide the node.
+If the node resides in a subdirectory,
+all parent directory nodes must be visible to be able to access the node.
 .El
 .Sh IMPLEMENTATION NOTES
 Rulesets are created by the kernel at the first reference