operations: ensure SrcFsType is set correctly when using --metadata-mapper

Before this change on files which have unknown length (like Google
Documents) the SrcFsType would be set to "memoryFs".

This change fixes the problem by getting the Copy function to pass the
src Fs into a variant of Rcat.

Fixes #7848

fs/operations/operations.go

@@ -1270,6 +1270,13 @@ func Cat(ctx context.Context, f fs.Fs, w io.Writer, offset, count int64, sep []b
 
 // Rcat reads data from the Reader until EOF and uploads it to a file on remote
 func Rcat(ctx context.Context, fdst fs.Fs, dstFileName string, in io.ReadCloser, modTime time.Time, meta fs.Metadata) (dst fs.Object, err error) {
+	return rcatSrc(ctx, fdst, dstFileName, in, modTime, meta, nil)
+}
+
+// rcatSrc reads data from the Reader until EOF and uploads it to a file on remote
+//
+// Pass in fsrc if known or nil if not
+func rcatSrc(ctx context.Context, fdst fs.Fs, dstFileName string, in io.ReadCloser, modTime time.Time, meta fs.Metadata, fsrc fs.Fs) (dst fs.Object, err error) {
 	ci := fs.GetConfig(ctx)
 	tr := accounting.Stats(ctx).NewTransferRemoteSize(dstFileName, -1, nil, fdst)
 	defer func() {
@@ -1322,7 +1329,7 @@ func Rcat(ctx context.Context, fdst fs.Fs, dstFileName string, in io.ReadCloser,
 	buf := make([]byte, ci.StreamingUploadCutoff)
 	if n, err := io.ReadFull(trackingIn, buf); err == io.EOF || err == io.ErrUnexpectedEOF {
 		fs.Debugf(fdst, "File to upload is small (%d bytes), uploading instead of streaming", n)
-		src := object.NewMemoryObject(dstFileName, modTime, buf[:n]).WithMetadata(meta)
+		src := object.NewMemoryObject(dstFileName, modTime, buf[:n]).WithMetadata(meta).SetFs(fsrc)
 		return Copy(ctx, fdst, nil, dstFileName, src)
 	}
 
@@ -1355,7 +1362,7 @@ func Rcat(ctx context.Context, fdst fs.Fs, dstFileName string, in io.ReadCloser,
 		return nil, err
 	}
 
-	objInfo := object.NewStaticObjectInfo(dstFileName, modTime, -1, false, nil, nil).WithMetadata(meta)
+	objInfo := object.NewStaticObjectInfo(dstFileName, modTime, -1, false, nil, fsrc).WithMetadata(meta)
 	if dst, err = fStreamTo.Features().PutStream(ctx, in, objInfo, options...); err != nil {
 		return dst, err
 	}