Upgrading Makefile to generate datastore v1beta3.

Also
- Removing `v1beta2` generated code and `.proto` file
- Adding new `.proto` files and generated code
- Adding `make_datastore_grpc.py` script to tear out the
  `protoc` inserted lines by the gRPC plugin
- Updating `rewrite_imports.py` to rewrite the datastore
  imports

.gitignore

@@ -53,3 +53,4 @@ scripts/pylintrc_reduced
 # Directories used for creating generated PB2 files
 generated_python/
 cloud-bigtable-client/
+googleapis-pb/

Makefile

@@ -1,8 +1,10 @@
 GENERATED_DIR=$(shell pwd)/generated_python
 BT_DIR=$(shell pwd)/gcloud/bigtable/_generated
+DS_DIR=$(shell pwd)/gcloud/datastore/_generated
 GRPC_PLUGIN=grpc_python_plugin
 PROTOC_CMD=protoc
 BT_PROTOS_DIR=$(shell pwd)/cloud-bigtable-client/bigtable-protos/src/main/proto
+DS_PROTOS_DIR=$(shell pwd)/googleapis-pb
 
 help:
 	@echo 'Makefile for gcloud-python Bigtable protos                      '
@@ -12,8 +14,12 @@ help:
 	@echo '   make clean                    Clean generated files          '
 
 generate:
-	[ -d cloud-bigtable-client ] || git clone https://github.com/GoogleCloudPlatform/cloud-bigtable-client
+	# Retrieve git repos that have our *.proto files.
+	[ -d cloud-bigtable-client ] || git clone https://github.com/GoogleCloudPlatform/cloud-bigtable-client --depth=1
 	cd cloud-bigtable-client && git pull origin master
+	[ -d googleapis-pb ] || git clone https://github.com/google/googleapis googleapis-pb --depth=1
+	cd googleapis-pb && git pull origin master
+	# Make the directory where our *_pb2.py files will go.
 	mkdir -p $(GENERATED_DIR)
 	# Generate all *_pb2.py files that require gRPC.
 	$(PROTOC_CMD) \
@@ -27,35 +33,50 @@ generate:
 	# Generate all *_pb2.py files that do not require gRPC.
 	$(PROTOC_CMD) \
 	    --proto_path=$(BT_PROTOS_DIR) \
+	    --proto_path=$(DS_PROTOS_DIR) \
 	    --python_out=$(GENERATED_DIR) \
 	    $(BT_PROTOS_DIR)/google/bigtable/v1/bigtable_data.proto \
 	    $(BT_PROTOS_DIR)/google/bigtable/v1/bigtable_service_messages.proto \
 	    $(BT_PROTOS_DIR)/google/bigtable/admin/cluster/v1/bigtable_cluster_data.proto \
 	    $(BT_PROTOS_DIR)/google/bigtable/admin/cluster/v1/bigtable_cluster_service_messages.proto \
 	    $(BT_PROTOS_DIR)/google/bigtable/admin/table/v1/bigtable_table_data.proto \
-	    $(BT_PROTOS_DIR)/google/bigtable/admin/table/v1/bigtable_table_service_messages.proto
+	    $(BT_PROTOS_DIR)/google/bigtable/admin/table/v1/bigtable_table_service_messages.proto \
+	    $(DS_PROTOS_DIR)/google/datastore/v1beta3/datastore.proto \
+	    $(DS_PROTOS_DIR)/google/datastore/v1beta3/entity.proto \
+	    $(DS_PROTOS_DIR)/google/datastore/v1beta3/query.proto
 	# Move the newly generated *_pb2.py files into our library.
 	mv $(GENERATED_DIR)/google/bigtable/v1/* $(BT_DIR)
 	mv $(GENERATED_DIR)/google/bigtable/admin/cluster/v1/* $(BT_DIR)
 	mv $(GENERATED_DIR)/google/bigtable/admin/table/v1/* $(BT_DIR)
+	mv $(GENERATED_DIR)/google/datastore/v1beta3/* $(DS_DIR)
 	# Remove all existing *.proto files before we replace
 	rm -f $(BT_DIR)/*.proto
+	rm -f $(DS_DIR)/*.proto
 	# Copy over the *.proto files into our library.
 	cp $(BT_PROTOS_DIR)/google/bigtable/v1/*.proto $(BT_DIR)
 	cp $(BT_PROTOS_DIR)/google/bigtable/admin/cluster/v1/*.proto $(BT_DIR)
 	cp $(BT_PROTOS_DIR)/google/bigtable/admin/table/v1/*.proto $(BT_DIR)
 	cp $(BT_PROTOS_DIR)/google/longrunning/operations.proto $(BT_DIR)
+	cp $(DS_PROTOS_DIR)/google/datastore/v1beta3/*.proto $(DS_DIR)
 	# Rename all *.proto files in our library with an
 	# underscore and remove executable bit.
 	cd $(BT_DIR) && \
 	    for filename in *.proto; do \
 	        chmod -x $$filename ; \
 	        mv $$filename _$$filename ; \
 	    done
+	cd $(DS_DIR) && \
+	    for filename in *.proto; do \
+	        chmod -x $$filename ; \
+	        mv $$filename _$$filename ; \
+	    done
 	# Separate the gRPC parts of the operations service from the
 	# non-gRPC parts so that the protos from `googleapis-common-protos`
 	# can be used without gRPC.
 	python scripts/make_operations_grpc.py
+	# Separate the gRPC parts of the datastore service from the
+	# non-gRPC parts so that the protos can be used without gRPC.
+	python scripts/make_datastore_grpc.py
 	# Rewrite the imports in the generated *_pb2.py files.
 	python scripts/rewrite_imports.py