@Override
	protected void programClosed(Program program) {
		if (primaryProgram == program) {
			primaryProgram.removeListener(this);
			if (secondaryDiffProgram != null) {
				closeProgram2();
			}
			actionManager.programClosed(program);
		}
	}
Creates the plugin for indicating program differences to the user.

@param tool the tool that owns this plugin.
Ghidra/Features/ProgramDiff/src/main/java/ghidra/app/plugin/core/diff/ProgramDiffPlugin.java