[FAB-9416]: Add gradle task to update protos

This commit adds new gradle task to download update proto files required
by project (currently handled manually). Hence allowing to run following
command to get updates:

     gradle :fabric-chaincode-protos:downloadProtoFiles

which will download all depencies *.proto into project sub folder to get
them compiled.

Change-Id: Iac03e08214667b0af42b13741e959f70b8a50a2b
Signed-off-by: Artem Barger <bartem@il.ibm.com>

Author: C0rWin

fabric-chaincode-protos/build.gradle

@@ -3,19 +3,35 @@
  *
  * SPDX-License-Identifier: Apache-2.0
  */
-
 apply plugin: 'com.google.protobuf'
+apply plugin: 'de.undercouch.download'
 
 repositories {
     maven { url "https://plugins.gradle.org/m2/" }
+    jcenter()
 }
 
+// Fabric branch to download proto files from
+def fabricBranch = 'release-1.1'
+// Fabric Github repository link
+def fabricRepo = 'https://raw.githubusercontent.com/hyperledger/fabric'
+def protosDir = 'src/main/protos'
+// List of files to download
+def protoFiles = ['protos/common/common.proto'                     : "$protosDir/common/common.proto",
+                  'protos/ledger/queryresult/kv_query_result.proto': "$protosDir/ledger/queryresult/kv_query_result.proto",
+                  'protos/peer/chaincode.proto'                    : "$protosDir/peer/chaincode.proto",
+                  'protos/peer/chaincode_event.proto'              : "$protosDir/peer/chaincode_event.proto",
+                  'protos/peer/chaincode_shim.proto'               : "$protosDir/peer/chaincode_shim.proto",
+                  'protos/peer/proposal.proto'                     : "$protosDir/peer/proposal.proto",
+                  'protos/peer/proposal_response.proto'            : "$protosDir/peer/proposal_response.proto"]
+
 buildscript {
     repositories {
         maven { url "https://plugins.gradle.org/m2/" }
     }
     dependencies {
         classpath 'com.google.protobuf:protobuf-gradle-plugin:0.8.5'
+        classpath 'de.undercouch:gradle-download-task:3.4.2'
     }
 }
 
@@ -54,7 +70,17 @@ sourceSets {
             srcDirs = ['src/main/java', 'src/main/grpc']
         }
         proto {
-            srcDirs 'src/main/proto'
+            srcDirs 'src/main/protos'
+        }
+    }
+}
+
+task downloadProtoFiles << {
+    protoFiles.each { k, v ->
+        download {
+            src "$fabricRepo/$fabricBranch/$k"
+            dest v
+            onlyIfModified true
         }
     }
 }