backend/layout: unexport fields and simplify rest layout

internal/backend/layout/layout_rest.go

@@ -1,18 +1,24 @@
 package layout
 
 import (
+	"path"
+
 	"github.com/restic/restic/internal/backend"
 )
 
 // RESTLayout implements the default layout for the REST protocol.
 type RESTLayout struct {
-	URL  string
-	Path string
-	Join func(...string) string
+	url string
 }
 
 var restLayoutPaths = defaultLayoutPaths
 
+func NewRESTLayout(url string) *RESTLayout {
+	return &RESTLayout{
+		url: url,
+	}
+}
+
 func (l *RESTLayout) String() string {
 	return "<RESTLayout>"
 }
@@ -25,10 +31,10 @@ func (l *RESTLayout) Name() string {
 // Dirname returns the directory path for a given file type and name.
 func (l *RESTLayout) Dirname(h backend.Handle) string {
 	if h.Type == backend.ConfigFile {
-		return l.URL + l.Join(l.Path, "/")
+		return l.url + "/"
 	}
 
-	return l.URL + l.Join(l.Path, "/", restLayoutPaths[h.Type]) + "/"
+	return l.url + path.Join("/", restLayoutPaths[h.Type]) + "/"
 }
 
 // Filename returns a path to a file, including its name.
@@ -39,18 +45,18 @@ func (l *RESTLayout) Filename(h backend.Handle) string {
 		name = "config"
 	}
 
-	return l.URL + l.Join(l.Path, "/", restLayoutPaths[h.Type], name)
+	return l.url + path.Join("/", restLayoutPaths[h.Type], name)
 }
 
 // Paths returns all directory names
 func (l *RESTLayout) Paths() (dirs []string) {
 	for _, p := range restLayoutPaths {
-		dirs = append(dirs, l.URL+l.Join(l.Path, p))
+		dirs = append(dirs, l.url+path.Join("/", p))
 	}
 	return dirs
 }
 
 // Basedir returns the base dir name for files of type t.
 func (l *RESTLayout) Basedir(t backend.FileType) (dirname string, subdirs bool) {
-	return l.URL + l.Join(l.Path, restLayoutPaths[t]), false
+	return l.url + path.Join("/", restLayoutPaths[t]), false
 }