S3: fix quota update after an upload error

S3 uploads are atomic, if the upload fails we have no partial file so we
have to update the user quota only if the upload succeed

sftpd/internal_test.go

@@ -425,6 +425,28 @@ func TestUploadFiles(t *testing.T) {
 	if err == nil {
 		t.Errorf("upload new file in missing path must fail")
 	}
+	c.fs = newMockOsFs(nil, nil, false, "123", os.TempDir())
+	f, _ := ioutil.TempFile("", "temp")
+	f.Close()
+	_, err = c.handleSFTPUploadToExistingFile(flags, f.Name(), f.Name(), 123)
+	if err != nil {
+		t.Errorf("unexpected error: %v", err)
+	}
+	if len(activeTransfers) != 1 {
+		t.Errorf("unexpected number of transfer, expected 1, current: %v", len(activeTransfers))
+	}
+	transfer := activeTransfers[0]
+	if transfer.initialSize != 123 {
+		t.Errorf("unexpected initial size: %v", transfer.initialSize)
+	}
+	err = transfer.Close()
+	if err != nil {
+		t.Errorf("unexpected error: %v", err)
+	}
+	if len(activeTransfers) != 0 {
+		t.Errorf("unexpected number of transfer, expected 0, current: %v", len(activeTransfers))
+	}
+	os.Remove(f.Name())
 	uploadMode = oldUploadMode
 }
 
@@ -899,6 +921,17 @@ func TestSystemCommandErrors(t *testing.T) {
 	}
 }
 
+func TestTransferUpdateQuota(t *testing.T) {
+	transfer := Transfer{
+		transferType:  transferUpload,
+		bytesReceived: 123,
+		lock:          new(sync.Mutex)}
+	transfer.TransferError(errors.New("fake error"))
+	if transfer.updateQuota(1) {
+		t.Errorf("update quota must fail, there is a error and this is a remote upload")
+	}
+}
+
 func TestGetConnectionInfo(t *testing.T) {
 	c := ConnectionStatus{
 		Username:      "test_user",
@@ -1222,6 +1255,10 @@ func TestSCPErrorsMockFs(t *testing.T) {
 	if err != errFake {
 		t.Errorf("unexpected error: %v", err)
 	}
+	err = scpCommand.handleUploadFile(testfile, testfile, 0, false, 4)
+	if err != nil {
+		t.Errorf("unexpected error: %v", err)
+	}
 	os.Remove(testfile)
 }