Clarify some arg counts and some related tests.

--HG--
extra : rebase_source : e50c757b46406988b0bfa0c179ec1e9bad21a446

common/modules/commands.jsm

@@ -1596,6 +1596,7 @@ var Commands = Module("commands", {
                 dactyl.echomsg(_("command.yank.yankedLine" + (lines == 1 ? "" : "s"), lines));
             },
             {
+                argCount: "1",
                 completer: function (context) modules.completion[/^:/.test(context.filter) ? "ex" : "javascript"](context),
                 literal: 0
             });

common/modules/io.jsm

@@ -841,7 +841,7 @@ unlet s:cpo_save
 
                 modules.autocommands.trigger("ShellCmdPost", {});
             }, {
-                argCount: "?", // TODO: "1" - probably not worth supporting weird Vim edge cases. The dream is dead. --djk
+                argCount: "1",
                 bang: true,
                 // This is abominably slow.
                 // completer: function (context) completion.shellCommand(context),

common/modules/javascript.jsm

@@ -842,6 +842,7 @@ var JavaScript = Module("javascript", {
                            .open();
                 }
             }, {
+                argCount: "?",
                 bang: true,
                 completer: function (context) modules.completion.javascript(context),
                 hereDoc: true,