How to keep Clover reports between builds?

If you want to keep Clover reports between builds, outside of source directory you can use <outputDirectory/> element in Clover configuration.

In your configuration put something like this:

<build>
 <plugins>
  <plugin>
   <artifactId>clover-maven-plugin</artifactId>
   <groupId>org.openclover</groupId>
   <configuration>
    <!-- Other configuration options -->

    <!-- Set output directory outside maven build -->
    <outputDirectory>c:\dev\cloverReport\${pom.artifactId}</outputDirectory>
   </configuration>
   <!-- Other elements -->
  </plugin>
 </plugins>
</build>

Use ${pom.artifactId} if you have multi module project - reports for each module will be placed in a separate directory.