These are the protobuf definition files used by hbase. ALL protobuf proto files
must live in this module whether test or spark or coprocessor endpoint protos
because we are being careful about what we expose of protobuf to downstreamers;
we are shading our version of protobuf so we can freely change it as needed.

The produced java classes are generated into
src/main/java/org/apache/hadoop/hbase/protobuf/generated
and then checked in.  The reasoning is that they change infrequently.

To regenerate the classes after making definition file changes, ensure first that
the protobuf protoc tool is in your $PATH. You may need to download it and build
it first; its part of the protobuf package. For example, if using v2.5.0 of
protobuf, it is obtainable from here:

 https://github.com/google/protobuf/releases/tag/v2.5.0

HBase uses hadoop-maven-plugins:protoc goal to invoke the protoc command. You can
compile the protoc definitions by invoking maven with profile compile-protobuf or
passing in compile-protobuf property.

mvn compile -Dcompile-protobuf
or
mvn compile -Pcompile-protobuf

You may also want to define protoc.path for the protoc binary

mvn compile -Dcompile-protobuf -Dprotoc.path=/opt/local/bin/protoc

If you have added a new proto file, you should add it to the pom.xml file first.
Other modules also support the maven profile.

After you've done the above, check it in and then check it in (or post a patch
on a JIRA with your definition file changes and the generated files).