Bug 123040 [Commands] request: display help topic
I'm going to attach a patch to "command-ify" the opening of help topics. The command takes a parameter which is the href of a help topic. The default handler uses IWorkbenchHelpSystem.displayHelpResource(String) with the href parameter. If no parameter was given, the default handler calls IWorkbenchHelpSystem.displayHelp() instead to simply open the help system. Note that this looks like it should be opened against User Assistance, but the plugins that should be patched (I think) are org.eclipse.ui and org.eclipse.ui.workbench, so I opened against UI.
bundles/org.eclipse.core.commands/src/org/eclipse/core/commands/ParameterizedCommand.java
return false;
		}
		return Util.equals(this.parameterizations, command.parameterizations);
	}
	/**
	 * Executes this command with its parameters. This method will succeed
	 * regardless of whether the command is enabled or defined. It is
	 * preferrable to use {@link #executeWithChecks(Object, Object)}.
	 * 
	 * @param trigger
	 *            The object that triggered the execution; may be
	 *            <code>null</code>.
	 * @param applicationContext
	 *            The state of the application at the time the execution was
	 *            triggered; may be <code>null</code>.
	 * @return The result of the execution; may be <code>null</code>.
	 * @throws ExecutionException
	 *             If the handler has problems executing this command.
	 * @throws NotHandledException
	 *             If there is no handler.
	 * @deprecated Please use {@link #executeWithChecks(Object, Object)}
	 *             instead.
	 */
	public final Object execute(final Object trigger,
			final Object applicationContext) throws ExecutionException,
			NotHandledException {
		return command.execute(new ExecutionEvent(command, getParameterMap(),
				trigger, applicationContext));
	}
	/**