chore(volumes): modify volumes:client cmd annotation and can not cp dir

Author: jianxiaoguo

cmd/volumes.go

@@ -291,6 +291,9 @@ func (d *DryccCmd) volumesClientCp(appID, src, dst string) error {
 		if err != nil {
 			return err
 		}
+		if urlpath == "" || urlpath == "/" {
+			return fmt.Errorf("path is a directory, not a file")
+		}
 		res, err := volumes.GetFile(s.Client, appID, name, urlpath)
 		if err != nil {
 			return err
@@ -302,7 +305,7 @@ func (d *DryccCmd) volumesClientCp(appID, src, dst string) error {
 				dst = path.Join(dst, arrays[len(arrays)-1])
 			}
 		}
-		w, err := os.OpenFile(dst, os.O_CREATE|os.O_WRONLY, 0644)
+		w, err := os.OpenFile(dst, os.O_CREATE|os.O_WRONLY|os.O_TRUNC, 0644)
 		if err != nil {
 			return err
 		}

parser/volumes.go

@@ -232,7 +232,8 @@ Arguments:
     cp         copy volume files
     rm         remove volume files
   <args>
-    arguments for running commands
+    arguments for running commands, when cmd is 'cp', args should be '[source] [dest]'.
+    volume path format 'vol://volumename/', '/' is equivalent to the mount path.
 
 Options:
   -a --app=<app>