test helpers: add RemoveAll and ResetReadOnly

This is mainly needed in Windows, where files and dirs cannot be
removed unless they are writeable.

test/helpers.go

@@ -59,6 +59,7 @@ func Equals(tb testing.TB, exp, act interface{}) {
 	}
 }
 
+// ParseID parses s as a backend.ID and panics if that fails.
 func ParseID(s string) backend.ID {
 	id, err := backend.ParseID(s)
 	if err != nil {
@@ -123,7 +124,7 @@ func WithTestEnvironment(t testing.TB, repoFixture string, f func(repodir string
 		return
 	}
 
-	OK(t, os.RemoveAll(tempdir))
+	RemoveAll(t, tempdir)
 }
 
 // OpenLocalRepo opens the local repository located at dir.
@@ -137,3 +138,31 @@ func OpenLocalRepo(t testing.TB, dir string) *repository.Repository {
 
 	return repo
 }
+
+func isFile(fi os.FileInfo) bool {
+	return fi.Mode()&(os.ModeType|os.ModeCharDevice) == 0
+}
+
+// ResetReadOnly recursively resets the read-only flag recursively for dir.
+// This is mainly used for tests on Windows, which is unable to delete a file
+// set read-only.
+func ResetReadOnly(t testing.TB, dir string) {
+	OK(t, filepath.Walk(dir, func(path string, fi os.FileInfo, err error) error {
+		if fi.IsDir() {
+			return os.Chmod(path, 0777)
+		}
+
+		if isFile(fi) {
+			return os.Chmod(path, 0666)
+		}
+
+		return nil
+	}))
+}
+
+// RemoveAll recursively resets the read-only flag of all files and dirs and
+// afterwards uses os.RemoveAll() to remove the path.
+func RemoveAll(t testing.TB, path string) {
+	ResetReadOnly(t, path)
+	OK(t, os.RemoveAll(path))
+}