gs: minor comment cleanups

* Remove a reference to S3.
* Config can only be used for GCS, not other "gcs compatibile servers".
* Make comments complete sentences.

internal/backend/gs/config.go

@@ -8,8 +8,8 @@ import (
 	"github.com/restic/restic/internal/options"
 )
 
-// Config contains all configuration necessary to connect to an gcs compatible
-// server.
+// Config contains all configuration necessary to connect to a Google Cloud
+// Storage bucket.
 type Config struct {
 	ProjectID   string
 	JSONKeyPath string

internal/backend/gs/gs.go

@@ -1,3 +1,4 @@
+// Package gs provides a restic backend for Google Cloud Storage.
 package gs
 
 import (
@@ -31,7 +32,7 @@ type Backend struct {
 	backend.Layout
 }
 
-// make sure that *Backend implements backend.Backend
+// Ensure that *Backend implements restic.Backend.
 var _ restic.Backend = &Backend{}
 
 func getStorageService(jsonKeyPath string) (*storage.Service, error) {
@@ -87,21 +88,20 @@ func open(cfg Config) (*Backend, error) {
 	return be, nil
 }
 
-// Open opens the gs backend at bucket and region.
+// Open opens the gs backend at the specified bucket.
 func Open(cfg Config) (restic.Backend, error) {
 	return open(cfg)
 }
 
-// Create opens the S3 backend at bucket and region and creates the bucket if
-// it does not exist yet.
+// Create opens the gs backend at the specified bucket and creates the bucket
+// if it does not exist yet.
 func Create(cfg Config) (restic.Backend, error) {
 	be, err := open(cfg)
-
 	if err != nil {
 		return nil, errors.Wrap(err, "open")
 	}
 
-	// Create bucket if not exists
+	// Create bucket if it doesn't exist.
 	if _, err := be.service.Buckets.Get(be.bucketName).Do(); err != nil {
 		bucket := &storage.Bucket{
 			Name: be.bucketName,
@@ -371,5 +371,5 @@ func (be *Backend) Delete(ctx context.Context) error {
 	return be.Remove(ctx, restic.Handle{Type: restic.ConfigFile})
 }
 
-// Close does nothing
+// Close does nothing.
 func (be *Backend) Close() error { return nil }