plumbing: packfile parser process deltaRef before deltaObj in thin pack

plumbing/format/packfile/parser.go

···
 
 		case ObjectSection:
 			oh := data.Value().(ObjectHeader)
-
 			if oh.Type.IsDelta() {
 				if oh.Type == plumbing.OFSDeltaObject {
 					pendingDeltas = append(pendingDeltas, &oh)
···
 		return plumbing.ZeroHash, ErrEmptyPackfile
 	}
 
-	for _, oh := range pendingDeltas {
+	for _, oh := range pendingDeltaREFs {
 		err := p.processDelta(oh)
 		if err != nil {
 			return plumbing.ZeroHash, err
 		}
 	}
 
-	for _, oh := range pendingDeltaREFs {
+	for _, oh := range pendingDeltas {
 		err := p.processDelta(oh)
 		if err != nil {
 			return plumbing.ZeroHash, err
···
 	// If the parent is not an external ref and we don't have the
 	// content offset, we won't be able to inflate via seeking through
 	// the packfile.
-	if parent.externalRef && parent.ContentOffset == 0 {
+	if !parent.externalRef && parent.ContentOffset == 0 {
 		return nil, plumbing.ErrObjectNotFound
 	}
 

plumbing/format/packfile/parser_test.go

···
 	assert.NoError(t, err)
 
 	_, err = parser.Parse()
-	assert.Equal(t, err, plumbing.ErrObjectNotFound)
+	assert.Equal(t, err, packfile.ErrReferenceDeltaNotFound)
 
 	// start over with a clean repo
 	r, err = git.PlainInit(t.TempDir(), true)