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
final int parameterizationCount = parameterizations.length;
			for (int i = 0; i < parameterizationCount; i++) {
				final Parameterization parameterization = parameterizations[i];
				nameBuffer.append(parameterization.getParameter().getName());
				nameBuffer.append(": "); 
				try {
					nameBuffer.append(parameterization.getValueName());
				} catch (final ParameterValuesException e) {
					/*
					 * Just let it go for now. If someone complains we can add
					 * more info later.
					 */
				}
				
				if (i + 1 < parameterizationCount) {
					nameBuffer.append(", "); 
				}
			}
			nameBuffer.append(')');
		}
		return nameBuffer.toString();
	}
	/**
	 * Returns the parameter map, as can be used to construct an
	 * <code>ExecutionEvent</code>.
	 * 
	 * @return The map of parameter ids (<code>String</code>) to parameter
	 *         values (<code>String</code>). This map is never
	 *         <code>null</code>, but may be empty.
	 */