man: Document dpkg-query --search and --listfiles output formats

Document or clarify the output formats, so that users can rely on it
instead of having to guess, and to make it explicit this can be relied
on.

Author: guillemj

man/dpkg-query.pod

@@ -142,8 +142,9 @@ on the argument list.
 List files installed to your system from I<package-name>. When multiple
 I<package-name>s are listed, the requested lists of files are separated
 by an empty line, with the same order as specified on the argument list.
-However, note that files created by package-specific installation-scripts
-are not listed.
+
+This command will not list extra files created by maintainer scripts,
+nor will it list alternatives.
 
 =item B<--control-list> I<package-name>
 
@@ -189,6 +190,14 @@ handled like a glob pattern, otherwise any trailing ‘B</>’ or
 This command will not list extra files created by maintainer scripts,
 nor will it list alternatives.
 
+The output format consists of one line per matching pattern, with a list
+of packages owning the pathname separated by a comma (U+002C ‘B<,>’) and
+a space (U+0020 ‘B< >’), followed by a colon (U+003A ‘B<:>’) and a space,
+followed by the pathname. As in:
+
+  pkgname1, pkgname2: pathname1
+  pkgname3: pathname2
+
 =item B<-p>, B<--print-avail> [I<package-name>...]
 
 Display details about packages, as found in I<%ADMINDIR%/available>.