Create separate interface for object information.

Take out read-only information about a Fs in a separate struct to limit access.

See discussion at #282.

drive/drive.go

@@ -84,7 +84,7 @@ var (
 
 // Register with Fs
 func init() {
-	fs.Register(&fs.Info{
+	fs.Register(&fs.RegInfo{
 		Name:  "drive",
 		NewFs: NewFs,
 		Config: func(name string) {
@@ -600,7 +600,11 @@ func (f *Fs) createFileInfo(remote string, modTime time.Time, size int64) (*Obje
 // Copy the reader in to the new object which is returned
 //
 // The new object may have been created if an error is returned
-func (f *Fs) Put(in io.Reader, remote string, modTime time.Time, size int64) (fs.Object, error) {
+func (f *Fs) Put(in io.Reader, src fs.ObjectInfo) (fs.Object, error) {
+	remote := src.Remote()
+	size := src.Size()
+	modTime := src.ModTime()
+
 	o, createInfo, err := f.createFileInfo(remote, modTime, size)
 	if err != nil {
 		return nil, err
@@ -818,7 +822,7 @@ func (f *Fs) Hashes() fs.HashSet {
 // ------------------------------------------------------------
 
 // Fs returns the parent Fs
-func (o *Object) Fs() fs.Fs {
+func (o *Object) Fs() fs.Info {
 	return o.fs
 }
 
@@ -1025,7 +1029,9 @@ func (o *Object) Open() (in io.ReadCloser, err error) {
 // Copy the reader into the object updating modTime and size
 //
 // The new object may have been created if an error is returned
-func (o *Object) Update(in io.Reader, modTime time.Time, size int64) error {
+func (o *Object) Update(in io.Reader, src fs.ObjectInfo) error {
+	size := src.Size()
+	modTime := src.ModTime()
 	if o.isDocument {
 		return fmt.Errorf("Can't update a google document")
 	}