Document --noremotedb flag for grpc_cli.

It's surprising that grpc_cli always attempts to use the reflection
service even when providing local proto files. Document the
existence of a flag that surpresses this behavior.

doc/command_line_tool.md

@@ -70,6 +70,8 @@ guides for
 , [C++](https://github.com/grpc/grpc/blob/master/doc/server_reflection_tutorial.md)
 and [Go](https://github.com/grpc/grpc-go/blob/master/Documentation/server-reflection-tutorial.md)
 
+Local proto files can be used as an alternative. See instructions [below](#Call-a-remote-method).
+
 ## Usage
 
 ### List services
@@ -185,6 +187,10 @@ We can send RPCs to a server and get responses using `grpc_cli call` command.
     If the proto file is not under the current directory, you can use
     `--proto_path` to specify a new search root.
 
+    Note that the tool will always attempt to use the reflection service first,
+    falling back to local proto files if the service is not found. Use
+    `--noremotedb` to avoid attempting to use the reflection service.
+
 -   Send non-proto rpc
 
     For using gRPC with protocols other than protobuf, you will need the exact

test/cpp/util/grpc_tool.cc

@@ -469,6 +469,8 @@ bool GrpcTool::CallMethod(int argc, const char** argv,
       " fallback when parsing request/response\n"
       "    --proto_path             ; The search path of proto files, valid"
       " only when --protofiles is given\n"
+      "    --noremotedb             ; Don't attempt to use reflection service"
+      " at all\n"
       "    --metadata               ; The metadata to be sent to the server\n"
       "    --infile                 ; Input filename (defaults to stdin)\n"
       "    --outfile                ; Output filename (defaults to stdout)\n"
@@ -810,6 +812,8 @@ bool GrpcTool::ParseMessage(int argc, const char** argv,
       " fallback when parsing request/response\n"
       "    --proto_path             ; The search path of proto files, valid"
       " only when --protofiles is given\n"
+      "    --noremotedb             ; Don't attempt to use reflection service"
+      " at all\n"
       "    --infile                 ; Input filename (defaults to stdin)\n"
       "    --outfile                ; Output filename (defaults to stdout)\n"
       "    --binary_input           ; Input in binary format\n"