dpkg-query(1): Add a new subsection to explain virtual fields

man/dpkg-query.1

@@ -1,4 +1,4 @@
-.TH dpkg\-query 1 "2011-08-14" "Debian Project" "dpkg suite"
+.TH dpkg\-query 1 "2012-01-11" "Debian Project" "dpkg suite"
 .SH NAME
 dpkg\-query \- a tool to query the dpkg database
 .
@@ -179,8 +179,15 @@ fields or fields stored in the binary package end up in it):
     \fBTriggers\-Awaited\fP (internal)
     \fBTriggers\-Pending\fP (internal)
     \fBVersion\fP
-    \fBshow:Summary\fP (virtual)
-    \fBshow:Status\-Abbrev\fP (virtual)
+.fi
+
+The following are virtual fields, generated by \fBdpkg\-query\fP from
+values from other fields (note that these do not use valid names for
+fields in control files):
+
+.nf
+    \fBshow:Summary\fP
+    \fBshow:Status\-Abbrev\fP
 .fi
 
 The default format string is \(lq\fB${Package}\et${Version}\en\fP\(rq.