Add c_<compl-{next,prev}-group> help entries.

common/content/commandline.js

@@ -1609,28 +1609,32 @@ var CommandLine = Module("commandline", {
                  self.completions.onTab(keypressEvents[0]);
              });
 
-        bind(["<C-Tab>", "<A-f>", "<compl-next-group>"], "Select the next matching completion group",
+        bind(["<C-Tab>", "<A-f>", "<compl-next-group>"],
+             "Select the next matching completion group",
              function ({ keypressEvents, self }) {
                  dactyl.assert(self.completions);
                  self.completions.tabTimer.flush();
                  self.completions.select(self.completions.CTXT_DOWN);
              });
 
-        bind(["<C-S-Tab>", "<A-S-f>", "<compl-prev-group>"], "Select the previous matching completion group",
+        bind(["<C-S-Tab>", "<A-S-f>", "<compl-prev-group>"],
+             "Select the previous matching completion group",
              function ({ keypressEvents, self }) {
                  dactyl.assert(self.completions);
                  self.completions.tabTimer.flush();
                  self.completions.select(self.completions.CTXT_UP);
              });
 
-        bind(["<C-f>", "<PageDown>", "<compl-next-page>"], "Select the next page of completions",
+        bind(["<C-f>", "<PageDown>", "<compl-next-page>"],
+             "Select the next page of completions",
              function ({ keypressEvents, self }) {
                  dactyl.assert(self.completions);
                  self.completions.tabTimer.flush();
                  self.completions.select(self.completions.PAGE_DOWN);
              });
 
-        bind(["<C-b>", "<PageUp>", "<compl-prev-page>"], "Select the previous page of completions",
+        bind(["<C-b>", "<PageUp>", "<compl-prev-page>"],
+             "Select the previous page of completions",
              function ({ keypressEvents, self }) {
                  dactyl.assert(self.completions);
                  self.completions.tabTimer.flush();

common/content/dactyl.js

@@ -695,6 +695,9 @@ var Dactyl = Module("dactyl", XPCOM(Ci.nsISupportsWeakReference, ModuleBase), {
         }
         else if (obj instanceof Map) {
             spec = function (map) obj.count ? <><oa>count</oa>{map}</> : <>{map}</>;
+            tag = function (map) <>{
+                    let (c = obj.modes[0].char) c ? c + "_" : ""
+                }{ map }</>;
             link = function (map) {
                 let [, mode, name, extra] = /^(?:(.)_)?(?:<([^>]+)>)?(.*)$/.exec(map);
                 let k = <k>{extra}</k>;

common/locale/en-US/cmdline.xml

@@ -161,6 +161,23 @@
     </description>
 </item>
 
+<item>
+    <tags><![CDATA[c_<A-f> c_<C-Tab> c_<compl-next-group>]]></tags>
+    <spec>&lt;C-Tab></spec>
+    <description>
+        <p>Select the next matching completion group.</p>
+    </description>
+</item>
+
+<item>
+    <tags><![CDATA[c_<A-S-F> c_<C-S-Tab> c_<compl-prev-group>]]></tags>
+    <spec>&lt;C-S-Tab></spec>
+    <description>
+        <p>Select the previous matching completion group.</p>
+    </description>
+</item>
+
+
 <h2 tag="cmdline-lines">Ex command lines</h2>
 
 <item>

common/modules/completion.jsm

@@ -643,7 +643,7 @@ var CompletionContext = Class("CompletionContext", {
     getRow: function getRow(idx, doc) {
         let cache = this.cache.rows;
         if (cache) {
-            if (!(idx in this.cache.rows))
+            if (idx in this.items && !(idx in this.cache.rows))
                 try {
                     cache[idx] = util.xmlToDom(this.createRow(this.items[idx]),
                                                doc || this.doc);