swarming: refactor cipd input

appengine/swarming/proto/config.proto

Index: appengine/swarming/proto/config.proto
diff --git a/appengine/swarming/proto/config.proto b/appengine/swarming/proto/config.proto
index b0406e9d3254eb97587cfa82757623fcac82f5e6..4c13479dddded0c75eb97d9d54ce213f577e7fe9 100644
--- a/appengine/swarming/proto/config.proto
+++ b/appengine/swarming/proto/config.proto
@@ -20,6 +20,9 @@ message SettingsCfg {
 
     // Configuration for swarming-isolate integration.
     optional IsolateSettings isolate = 5;
+
+    // Configuration for swarming-cipd integration.
+    optional CipdSettings cipd = 6;
 }
 
 // Configuration for swarming-isolate integration.
@@ -33,3 +36,22 @@ message IsolateSettings {
     // 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;
+}