diff --git a/cmd/joj3/main.go b/cmd/joj3/main.go
index a3930b6..026dc06 100644
--- a/cmd/joj3/main.go
+++ b/cmd/joj3/main.go
@@ -39,9 +39,27 @@ func getCommitMsg() (string, error) {
 		slog.Error("get commit msg", "error", err)
 		return "", err
 	}
+	env.Attr.CommitMsg = commitMsg
 	return commitMsg, nil
 }
 
+func getConf(commitMsg string) (*joj3Conf.Conf, *joj3Conf.ConventionalCommit, error) {
+	confPath, confStat, conventionalCommit, err := getConfPath(commitMsg)
+	if err != nil {
+		return nil, nil, err
+	}
+	conf, err := loadConf(confPath)
+	if err != nil {
+		return nil, nil, err
+	}
+	env.Attr.ConfName = conf.Name
+	env.Attr.OutputPath = conf.Stage.OutputPath
+	if err := showConfStat(confPath, confStat); err != nil {
+		return nil, nil, err
+	}
+	return conf, conventionalCommit, nil
+}
+
 func getConfPath(commitMsg string) (string, fs.FileInfo, *joj3Conf.ConventionalCommit, error) {
 	confPath, confStat, conventionalCommit, err := joj3Conf.GetConfPath(
 		confFileRoot, confFileName, fallbackConfFileName, commitMsg, tag,
@@ -120,23 +138,13 @@ func mainImpl() (err error) {
 	if err != nil {
 		return err
 	}
-	env.Attr.CommitMsg = commitMsg
-	confPath, confStat, conventionalCommit, err := getConfPath(commitMsg)
+	conf, conventionalCommit, err := getConf(commitMsg)
 	if err != nil {
 		return err
 	}
-	conf, err := loadConf(confPath)
-	if err != nil {
-		return err
-	}
-	env.Attr.ConfName = conf.Name
-	env.Attr.OutputPath = conf.Stage.OutputPath
 	if err := setupSlog(conf); err != nil {
 		return err
 	}
-	if err := showConfStat(confPath, confStat); err != nil {
-		return err
-	}
 	if err := validateConf(conf); err != nil {
 		return err
 	}
diff --git a/cmd/joj3/stage.go b/cmd/joj3/stage.go
index c993925..da9e328 100644
--- a/cmd/joj3/stage.go
+++ b/cmd/joj3/stage.go
@@ -17,6 +17,27 @@ import (
 
 type StageResult stage.StageResult
 
+func newStageCmd(defaultCmd stage.Cmd, optionalCmd conf.OptionalCmd) (stage.Cmd, error) {
+	var cmd stage.Cmd
+	err := copier.CopyWithOption(
+		&cmd,
+		&defaultCmd,
+		copier.Option{DeepCopy: true},
+	)
+	if err != nil {
+		return cmd, err
+	}
+	err = copier.CopyWithOption(
+		&cmd,
+		&optionalCmd,
+		copier.Option{DeepCopy: true, IgnoreEmpty: true},
+	)
+	if err != nil {
+		return cmd, err
+	}
+	return cmd, nil
+}
+
 func generateStages(confStages []conf.ConfStage, groups []string) (
 	[]stage.Stage, error,
 ) {
@@ -45,71 +66,17 @@ func generateStages(confStages []conf.ConfStage, groups []string) (
 		existNames[s.Name] = true
 		var cmds []stage.Cmd
 		defaultCmd := s.Executor.With.Default
-		for _, optionalCmd := range s.Executor.With.Cases {
-			var cmd stage.Cmd
-			err := copier.CopyWithOption(
-				&cmd,
-				&defaultCmd,
-				copier.Option{DeepCopy: true},
-			)
-			if err != nil {
-				slog.Error("generate stages", "error", err)
-				return stages, err
-			}
-			err = copier.CopyWithOption(
-				&cmd,
-				&optionalCmd,
-				copier.Option{DeepCopy: true},
-			)
-			if err != nil {
-				slog.Error("generate stages", "error", err)
-				return stages, err
-			}
-			// since these 3 values are pointers, copier will always copy
-			// them, so we need to check them manually
-			if defaultCmd.Stdin != nil && optionalCmd.Stdin == nil {
-				var stdin stage.CmdFile
-				err := copier.CopyWithOption(
-					&stdin,
-					defaultCmd.Stdin,
-					copier.Option{DeepCopy: true},
-				)
-				if err != nil {
-					slog.Error("generate stages", "error", err)
-					return stages, err
-				}
-				cmd.Stdin = &stdin
-			}
-			if defaultCmd.Stdout != nil && optionalCmd.Stdout == nil {
-				var stdout stage.CmdFile
-				err := copier.CopyWithOption(
-					&stdout,
-					defaultCmd.Stdout,
-					copier.Option{DeepCopy: true},
-				)
-				if err != nil {
-					slog.Error("generate stages", "error", err)
-					return stages, err
-				}
-				cmd.Stdout = &stdout
-			}
-			if defaultCmd.Stderr != nil && optionalCmd.Stderr == nil {
-				var stderr stage.CmdFile
-				err := copier.CopyWithOption(
-					&stderr,
-					defaultCmd.Stderr,
-					copier.Option{DeepCopy: true},
-				)
-				if err != nil {
-					slog.Error("generate stages", "error", err)
-					return stages, err
-				}
-				cmd.Stderr = &stderr
-			}
-			cmds = append(cmds, cmd)
-		}
 		if len(s.Executor.With.Cases) == 0 {
 			cmds = []stage.Cmd{defaultCmd}
+		} else {
+			for _, optionalCmd := range s.Executor.With.Cases {
+				cmd, err := newStageCmd(defaultCmd, optionalCmd)
+				if err != nil {
+					slog.Error("generate stages", "error", err)
+					return stages, err
+				}
+				cmds = append(cmds, cmd)
+			}
 		}
 		parsers := []stage.StageParser{}
 		for _, p := range s.Parsers {