cipd: Implement local cache for ResolveVersion(...) call with tags.

go/src/infra/tools/cipd/apps/cipd/main.go

Index: go/src/infra/tools/cipd/apps/cipd/main.go
diff --git a/go/src/infra/tools/cipd/apps/cipd/main.go b/go/src/infra/tools/cipd/apps/cipd/main.go
index d33f4a841e9b1993a61593dacc715f61e97a06c0..e2b5744e55ed0f9ba7c23af84fd94e37309fa214 100644
--- a/go/src/infra/tools/cipd/apps/cipd/main.go
+++ b/go/src/infra/tools/cipd/apps/cipd/main.go
@@ -658,6 +658,7 @@ func ensurePackages(root string, desiredStateFile string, serviceOpts ServiceOpt
 	if err != nil {
 		return nil, err
 	}
+	defer client.Close()
 	desiredState, err := client.ProcessEnsureFile(f)
 	if err != nil {
 		return nil, err
@@ -703,6 +704,7 @@ func resolveVersion(packagePrefix, version string, serviceOpts ServiceOptions) (
 	if err != nil {
 		return nil, err
 	}
+	defer client.Close()
 	return performBatchOperation(batchOperation{
 		client:        client,
 		packagePrefix: packagePrefix,
@@ -752,6 +754,7 @@ func setRef(packagePrefix, version string, refsOpts RefsOptions, serviceOpts Ser
 	if err != nil {
 		return nil, err
 	}
+	defer client.Close()
 
 	// Do not touch anything if some packages do not have requested version. So
 	// resolve versions first and only then move refs.
@@ -834,6 +837,7 @@ func listPackages(path string, recursive bool, serviceOpts ServiceOptions) ([]st
 	if err != nil {
 		return nil, err
 	}
+	defer client.Close()
 	packages, err := client.ListPackages(path, recursive)
 	if err != nil {
 		return nil, err
@@ -880,6 +884,7 @@ func listACL(packagePath string, serviceOpts ServiceOptions) error {
 	if err != nil {
 		return err
 	}
+	defer client.Close()
 	acls, err := client.FetchACL(packagePath)
 	if err != nil {
 		return err
@@ -996,6 +1001,7 @@ func editACL(packagePath string, owners, writers, readers, revoke principalsList
 	if err != nil {
 		return err
 	}
+	defer client.Close()
 	err = client.ModifyACL(packagePath, changes)
 	if err != nil {
 		return err
@@ -1137,6 +1143,7 @@ func fetchInstanceFile(packageName, version, instanceFile string, serviceOpts Se
 	if err != nil {
 		return common.Pin{}, err
 	}
+	defer client.Close()
 	pin, err := client.ResolveVersion(packageName, version)
 	if err != nil {
 		return common.Pin{}, err
@@ -1267,6 +1274,7 @@ func registerInstanceFile(instanceFile string, refsOpts RefsOptions, tagsOpts Ta
 	if err != nil {
 		return common.Pin{}, err
 	}
+	defer client.Close()
 	inspectInstance(inst, false)
 	err = client.RegisterInstance(inst)
 	if err != nil {
@@ -1323,6 +1331,7 @@ func tagPackage(packageName, version string, tagsOpts TagsOptions, serviceOpts S
 	if err != nil {
 		return common.Pin{}, err
 	}
+	defer client.Close()
 	pin, err := client.ResolveVersion(packageName, version)
 	if err != nil {
 		return common.Pin{}, err