feat: add localWriter

We add localWriter to wrap writer in the content store to
make sure not to write any labels in boltdb.
In that case, we can make gc work well with the lease.

Signed-off-by: Yadong Ding <ding_yadong@foxmail.com>

pkg/content/content.go

@@ -162,36 +162,37 @@ func (content *Content) Abort(ctx context.Context, ref string) error {
 
 func (content *Content) Writer(ctx context.Context, opts ...content.WriterOpt) (content.Writer, error) {
 	writer, err := content.store.Writer(ctx, opts...)
-	return &LocalWriter{
+	return &localWriter{
 		writer: writer,
 	}, err
 }
 
-type LocalWriter struct {
+// localWriter wrap the content.Writer
+type localWriter struct {
 	writer content.Writer
 }
 
-func (localWriter *LocalWriter) Close() error {
+func (localWriter *localWriter) Close() error {
 	return localWriter.writer.Close()
 }
 
-func (localWriter *LocalWriter) Write(p []byte) (int, error) {
+func (localWriter *localWriter) Write(p []byte) (int, error) {
 	return localWriter.writer.Write(p)
 }
 
-func (localWriter *LocalWriter) Digest() digest.Digest {
+func (localWriter *localWriter) Digest() digest.Digest {
 	return localWriter.writer.Digest()
 }
 
-func (localWriter *LocalWriter) Truncate(size int64) error {
+func (localWriter *localWriter) Truncate(size int64) error {
 	return localWriter.writer.Truncate(size)
 }
 
-func (localWriter *LocalWriter) Commit(ctx context.Context, size int64, expected digest.Digest, opts ...content.Opt) error {
+func (localWriter *localWriter) Commit(ctx context.Context, size int64, expected digest.Digest, opts ...content.Opt) error {
 	// we don't write any lables, drop the opts
 	return localWriter.writer.Commit(ctx, size, expected)
 }
 
-func (localWriter *LocalWriter) Status() (st content.Status, err error) {
+func (localWriter *localWriter) Status() (st content.Status, err error) {
 	return localWriter.writer.Status()
 }