spanner: add exported SetGoogleClientInfo wrapper to manual file

Make the generated setGoogleClientInfo package internal.

Remove spanner from post-processing list per #1924.

Change-Id: Ic4bc80560ec227ca794d7696f9d8a6375fac3841
Reviewed-on: https://code-review.googlesource.com/c/gocloud/+/54771
Reviewed-by: kokoro <noreply+kokoro@google.com>
Reviewed-by: Chris Broadfoot <cbro@google.com>
diff --git a/internal/gapicgen/generator/config.go b/internal/gapicgen/generator/config.go
index d5dd77a..c334cd5 100644
--- a/internal/gapicgen/generator/config.go
+++ b/internal/gapicgen/generator/config.go
@@ -692,6 +692,5 @@
 	"logging/apiv2",
 	"longrunning/autogen",
 	"pubsub/apiv1",
-	"spanner/apiv1",
 	"trace/apiv1",
 }
diff --git a/spanner/apiv1/info.go b/spanner/apiv1/info.go
new file mode 100644
index 0000000..4b7b796
--- /dev/null
+++ b/spanner/apiv1/info.go
@@ -0,0 +1,24 @@
+// Copyright 2020 Google LLC
+//
+// Licensed under the Apache License, Version 2.0 (the "License");
+// you may not use this file except in compliance with the License.
+// You may obtain a copy of the License at
+//
+//      http://www.apache.org/licenses/LICENSE-2.0
+//
+// Unless required by applicable law or agreed to in writing, software
+// distributed under the License is distributed on an "AS IS" BASIS,
+// WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+// See the License for the specific language governing permissions and
+// limitations under the License.
+
+package spanner
+
+// SetGoogleClientInfo sets the name and version of the application in
+// the `x-goog-api-client` header passed on each request. Also passes any
+// provided key-value pairs. Intended for use by Google-written clients.
+//
+// Internal use only.
+func (c *Client) SetGoogleClientInfo(keyval ...string) {
+	c.setGoogleClientInfo(keyval...)
+}
diff --git a/spanner/apiv1/spanner_client.go b/spanner/apiv1/spanner_client.go
index 1029f5c..cc2fe11 100644
--- a/spanner/apiv1/spanner_client.go
+++ b/spanner/apiv1/spanner_client.go
@@ -259,7 +259,7 @@
 
 		client: spannerpb.NewSpannerClient(connPool),
 	}
-	c.SetGoogleClientInfo()
+	c.setGoogleClientInfo()
 
 	return c, nil
 }
@@ -277,10 +277,10 @@
 	return c.connPool.Close()
 }
 
-// SetGoogleClientInfo sets the name and version of the application in
+// setGoogleClientInfo sets the name and version of the application in
 // the `x-goog-api-client` header passed on each request. Intended for
 // use by Google-written clients.
-func (c *Client) SetGoogleClientInfo(keyval ...string) {
+func (c *Client) setGoogleClientInfo(keyval ...string) {
 	kv := append([]string{"gl-go", versionGo()}, keyval...)
 	kv = append(kv, "gapic", versionClient, "gax", gax.Version, "grpc", grpc.Version)
 	c.xGoogMetadata = metadata.Pairs("x-goog-api-client", gax.XGoogHeader(kv...))