jenkins Email-ext plugin插件中Pre-send Script设置说明

在使用jenkins Email-ext plugin发送邮件时，项目中使用了SVN去同步，发现每次有同步，都会发送邮件，现只想SVN只更新，不发送邮件通知，这就要在Pre-send中做修改

看看官网说明：

Pre-send Script
The pre-send script is a feature which allows you to write a script that can modify the MimeMessage object prior to sending. This would allow adding custom headers, modifying the body, etc. Predefined variables include:
msg - the MimeMessage object which can be modified
logger - a PrintStream and will write to the job's log. 
build - the build this message belongs to
cancel - a boolean, which when set to true will cancel the sending of the email

　　只官网中可以看到cancel可以满足我们的需求，只要设置cancel为true就行，怎么设置呢？

下面这样写吗？

Jenkins > Manage > script 
if (build.changeSet.emptySet) cancel=true;

　　好像也不对，在多次尝试后，发出其实只需要这样写就可以

如下图：