add "?" as the argCount to commands with an optional single arg

content/bookmarks.js

@@ -341,6 +341,7 @@ function Bookmarks() //{{{
             liberator.echo(deletedCount + " bookmark(s) with url `" + url + "' deleted", commandline.FORCE_SINGLELINE);
         },
         {
+            argCount: "?",
             completer: function completer(context) completion.bookmark(context),
             literal: 0
         });
@@ -660,6 +661,7 @@ function History() //{{{
             }
         },
         {
+            argCount: "?",
             bang: true,
             completer: function completer(context)
             {
@@ -712,6 +714,7 @@ function History() //{{{
             }
         },
         {
+            argCount: "?",
             bang: true,
             completer: function completer(context)
             {

content/buffer.js

@@ -523,6 +523,7 @@ function Buffer() //{{{
             window.stylesheetSwitchAll(window.content, args);
         },
         {
+            argCount: "?",
             completer: function (context) completion.alternateStylesheet(context),
             literal: 0
         });

content/io.js

@@ -367,6 +367,7 @@ function IO() //{{{
             autocommands.trigger("ShellCmdPost", {});
         },
         {
+            argCount: "?", // TODO: "1" - probably not worth supporting weird Vim edge cases. The dream is dead. --djk
             bang: true,
             completer: function (context) completion.shellCommand(context),
             literal: 0

content/liberator.js

@@ -273,7 +273,7 @@ const liberator = (function () //{{{
                 }
             },
             {
-                argCount: "+",
+                argCount: "1",
                 // TODO: add this as a standard menu completion function
                 completer: function (context)
                 {
@@ -326,9 +326,10 @@ const liberator = (function () //{{{
                 liberator.help(args.string);
             },
             {
+                argCount: "?",
                 bang: true,
                 completer: function (context) completion.help(context),
-                literal: 0
+                literal: 0 // FIXME: why literal?
             });
 
         commands.add(["javas[cript]", "js"],

content/tabs.js

@@ -472,6 +472,7 @@ function Tabs() //{{{
                 }
             },
             {
+                argCount: "?",
                 bang: true,
                 count: true,
                 completer: function (context) completion.buffer(context),
@@ -481,7 +482,10 @@ function Tabs() //{{{
         commands.add(["buffers", "files", "ls", "tabs"],
             "Show a list of all buffers",
             function (args) { tabs.list(args.literalArg); },
-            { literal: 0 });
+            {
+                argCount: "?",
+                literal: 0
+            });
 
         commands.add(["quita[ll]", "qa[ll]"],
             "Quit " + config.name,
@@ -608,6 +612,7 @@ function Tabs() //{{{
                 window.undoCloseTab(count - 1);
             },
             {
+                argCount: "?",
                 completer: function (context)
                 {
                     context.keys = { text: function (item) item.state.entries[0].url, description: "title" };

content/vimperator.js

@@ -340,7 +340,7 @@ const config = { //{{{
                 liberator.echoerr("No sidebar " + args + " found");
             },
             {
-                argCount: "+",
+                argCount: "1",
                 completer: function (context) completion.sidebar(context),
                 literal: 0
             });