Add "none" compression type (#457)

* Add "none" compression type

* Add "none" compression to docs

* Use passThroughWriteCloser for "none" compression

* Add test for none compression

---------

Co-authored-by: Frederik Ring <frederik.ring@gmail.com>

cmd/backup/archive.go

@@ -93,6 +93,8 @@ func compress(paths []string, outFilePath, algo string, concurrency int) error {
 
 func getCompressionWriter(file *os.File, algo string, concurrency int) (io.WriteCloser, error) {
 	switch algo {
+	case "none":
+		return &passThroughWriteCloser{file}, nil
 	case "gz":
 		w, err := pgzip.NewWriterLevel(file, 5)
 		if err != nil {
@@ -165,3 +167,15 @@ func writeTarball(path string, tarWriter *tar.Writer, prefix string) error {
 
 	return nil
 }
+
+type passThroughWriteCloser struct {
+	target io.WriteCloser
+}
+
+func (p *passThroughWriteCloser) Write(b []byte) (int, error) {
+	return p.target.Write(b)
+}
+
+func (p *passThroughWriteCloser) Close() error {
+	return nil
+}

cmd/backup/config.go

@@ -92,7 +92,7 @@ type CompressionType string
 
 func (c *CompressionType) Decode(v string) error {
 	switch v {
-	case "gz", "zst":
+	case "none", "gz", "zst":
 		*c = CompressionType(v)
 		return nil
 	default:

cmd/backup/script.go

@@ -86,7 +86,12 @@ func (s *script) init() error {
 
 	var bf bytes.Buffer
 	if tErr := tmplFileName.Execute(&bf, map[string]string{
-		"Extension": fmt.Sprintf("tar.%s", s.c.BackupCompression),
+		"Extension": func() string {
+			if s.c.BackupCompression == "none" {
+				return "tar"
+			}
+			return fmt.Sprintf("tar.%s", s.c.BackupCompression)
+		}(),
 	}); tErr != nil {
 		return errwrap.Wrap(tErr, "error executing backup file extension template")
 	}