swarming: refactor cipd input

appengine/swarming/proto/config.proto

 // Copyright 2016 The LUCI Authors. All rights reserved.
 // Use of this source code is governed by the Apache v2.0 license that can be
 // found in the LICENSE file.
 
 syntax = "proto2";
 
 // Schema for settings.cfg service config file in luci-config.
 message SettingsCfg {
     // id to inject into pages if applicable.
     optional string google_analytics = 1;
 
     // The number of seconds an old task can be deduped from.
     optional int32 reusable_task_age_secs = 2;
 
     // The amount of time that has to pass before a machine is considered dead.
     optional int32 bot_death_timeout_secs = 3;
 
     // Enable ts_mon based monitoring.
     optional bool enable_ts_monitoring = 4;
 
     // Configuration for swarming-isolate integration.
     optional IsolateSettings isolate = 5;
+
+    // Configuration for swarming-cipd integration.
+    optional CipdSettings cipd = 6;
 }
 
 // Configuration for swarming-isolate integration.
 message IsolateSettings {
     // URL of the default isolate server to use if it is not specified in a
     // task. Must start with "https://" or "http://".
     // e.g. "https://isolateserver.appspot.com"
     optional string default_server = 1;
 
     // Default namespace to use if it is not specified in a task,
     // e.g. "default-gzip"
     optional string default_namespace = 2;
 }
+
+// Settings for Swarming-CIPD integration.
+//
+// WARNING: this message is embedded in task properties so
+// 1. Do not change field numbers
+// 2. Keep it small.
+message CipdSettings {
+    // Hostname of the cipd server, e.g. chrome-infra-packages.appspot.com.
+    optional string server_host = 1;
+
+    // Package name template for the CIPD client. MUST use ${platform} param.
+    // Will be used for https://{server_host}/_ah/api/repo/v1/client endpoint
+    // to fetch the cipd client.
+    optional string client_package_name = 2;
+
+    // Version of CIPD client to install. MUST be valid for all packages
+    // matched by client_package_name.
+    optional string client_package_version = 3;
+}