Fail build when license headers are omitted from a file

[snkinard]

From @shawnsmith:

It's really common to forget to keep license headers up-to-date as code evolves. So when you're adding them to all the files I strongly suggest you look into something like http://creadur.apache.org/rat/ to fail the build when license headers are omitted. For example:

   <build>
      <plugins>
        <plugin>
          <groupId>org.apache.rat</groupId>
          <artifactId>apache-rat-plugin</artifactId>
          <version>0.9</version>
          <configuration>
            <excludes>
            <exclude>.git/**</exclude>
            <exclude>.gitignore</exclude>
            <exclude>**/resources/*.txt</exclude>
            </excludes>
          </configuration>
          <executions>
            <execution>
              <id>rat-check</id>
              <phase>test</phase>
              <goals>
                <goal>check</goal>
              </goals>
            </execution>
          </executions>
        </plugin>
  ...

See also http://creadur.apache.org/rat/apache-rat-plugin/examples/custom-license.html

[snkinard]

Starting work on this.