Add test.Helper, also works with Go 1.8

internal/repository/testing.go

@@ -42,6 +42,7 @@ const testChunkerPol = chunker.Pol(0x3DA3358B4DC173)
 // password. If be is nil, an in-memory backend is used. A constant polynomial
 // is used for the chunker and low-security test parameters.
 func TestRepositoryWithBackend(t testing.TB, be restic.Backend) (r restic.Repository, cleanup func()) {
+	test.Helper(t).Helper()
 	TestUseLowSecurityKDFParameters(t)
 	restic.TestDisableCheckPolynomial(t)
 
@@ -70,6 +71,7 @@ func TestRepositoryWithBackend(t testing.TB, be restic.Backend) (r restic.Reposi
 // a non-existing directory, a local backend is created there and this is used
 // instead. The directory is not removed, but left there for inspection.
 func TestRepository(t testing.TB) (r restic.Repository, cleanup func()) {
+	test.Helper(t).Helper()
 	dir := os.Getenv("RESTIC_TEST_REPO")
 	if dir != "" {
 		_, err := os.Stat(dir)