wdcli: Implement backup & snapshot

This commit implements command backup and snapshot.

internal/targz/targz.go

@@ -11,11 +11,11 @@ import (
 
 // Package packages the directory src into dst.
 // onCopy, when not nil, is called for each file being copied into the archive.
-func Package(dst, src string, onCopy func(src string)) error {
+func Package(dst, src string, onCopy func(rel string, src string)) (count int64, err error) {
 	// create the target archive
 	archive, err := os.Create(dst)
 	if err != nil {
-		return err
+		return 0, err
 	}
 	defer archive.Close()
 
@@ -28,21 +28,28 @@ func Package(dst, src string, onCopy func(src string)) error {
 	defer tarHandle.Close()
 
 	// and walk through it!
-	return filepath.Walk(src, func(path string, info fs.FileInfo, err error) error {
-		if onCopy != nil {
-			onCopy(path)
-		}
-
+	err = filepath.Walk(src, func(path string, info fs.FileInfo, err error) error {
 		if err != nil {
 			return err
 		}
 
+		// determine the relative path
+		var relpath string
+		relpath, err = filepath.Rel(src, path)
+		if err != nil {
+			return err
+		}
+
+		if onCopy != nil {
+			onCopy(relpath, path)
+		}
+
 		// create a file info header!
-		tInfo, err := tar.FileInfoHeader(info, path)
+		tInfo, err := tar.FileInfoHeader(info, relpath)
 		if err != nil {
 			return err
 		}
-		tInfo.Name = filepath.ToSlash(path)
+		tInfo.Name = filepath.ToSlash(relpath)
 
 		// write it!
 		if err := tarHandle.WriteHeader(tInfo); err != nil {
@@ -62,8 +69,9 @@ func Package(dst, src string, onCopy func(src string)) error {
 		defer handle.Close()
 
 		// and copy it into the archive
-		_, err = io.Copy(tarHandle, handle)
+		ccount, err := io.Copy(tarHandle, handle)
+		count += ccount
 		return err
 	})
-
+	return
 }