directive-index: add UDEV fields

Makefile.am

@@ -701,7 +701,8 @@ XML_DIRECTIVE_FILES = \
 	man/systemd.path.xml \
 	man/systemd.timer.xml \
 	man/systemd.snapshot.xml \
-	man/systemd.exec.xml
+	man/systemd.exec.xml \
+	man/systemd.device.xml
 
 man/systemd.directives.xml: make-directive-index.py $(XML_DIRECTIVE_FILES)
 	$(AM_V_at)$(MKDIR_P) $(dir $@)

make-directive-index.py

@@ -38,6 +38,15 @@ TEMPLATE = '''\
 
                 <variablelist id='unit-directives' />
         </refsect1>
+
+        <refsect1>
+                <title>UDEV directives</title>
+
+                <para>Directives for configuring systemd units through the
+                udev database.</para>
+
+                <variablelist id='udev-directives' />
+        </refsect1>
 </refentry>
 '''
 
@@ -91,6 +100,7 @@ def make_page(xml_files):
     "Extract directives from xml_files and return XML index tree."
     directive_groups = {name:collections.defaultdict(list)
                         for name in ['unit-directives',
+                                     'udev-directives',
                                      ]}
     for page in xml_files:
         _extract_directives(directive_groups, page)

man/systemd.device.xml

@@ -96,7 +96,7 @@
                 database (which is recommended). The following udev
                 properties are understood by systemd:</para>
 
-                <variablelist>
+                <variablelist class='udev-directives'>
                         <varlistentry>
                                 <term><varname>SYSTEMD_WANTS=</varname></term>
                                 <listitem><para>Adds dependencies of