How to update the C++ sources of gRPC:

1. git clone http://github.com/grpc/grpc.git in a convenient directory
2. git checkout <tag> (current is release-0_13, commithash 78e04bbd)
3. mkdir -p third_party/grpc/src
4. cp -R <gRPC git tree>/src/{compiler,core-cpp} third_party/grpc/src
5. cp -R <gRPC git tree>/include third_party/grpc
6. Update BUILD files by copying the rules from the BUILD file of gRPC
7. Patch in grpc.patch. It makes gRPC work under msys2.

How to update the Java plugin:

For any architecture other than 64-bit Linux, downloading it from Maven Central is fine. For 64-bit Linux, the plugin needs to be built statically:

1. git clone http://github.com/grpc/grpc-java
2. git checkout <tag> (current is v0.13.2, commithash 5933cea9)
3. Modify the linker args in compiler/build.gradle according to the instructions below
4. Download the sources of protobuf (see third_party/protobuf/README.md) and compile it
5. export LDFLAGS=<protobuf dir>/src/.libs
6. export CXXFLAGS=<protobuf dir>/src
7. cd compiler; ../gradlew java_pluginExecutable

In compiler/build.gradle, this list of linker arguments:

          linker.args "-Wl,-Bstatic", "-lprotoc", "-lprotobuf", "-static-libgcc",
                      "-static-libstdc++",
                      "-Wl,-Bdynamic", "-lpthread", "-s"

needs to be replaced with this:

          linker.args "-Wl,-Bstatic", "-lprotoc", "-lprotobuf", "-static-libgcc",
                      "-static-libstdc++",
                      "-lpthread", "-lc", "-s", "-static"

How to update the Java code:

Simply download from Maven Central.