Specify return value where named return value is used

After [v0.9.0](https://github.com/mvdan/gofumpt/releases/tag/v0.9.0),
gofumpt prohibits "naked return" for the sake of clarity. This makes
more readable when "named return value" is used.
For more infomation for "prohibition of naked return":
https://github.com/mvdan/gofumpt/issues/285.

pkg/commands/oscommands/copy.go

@@ -35,16 +35,16 @@ import (
 // destination file exists, all it's contents will be replaced by the contents
 // of the source file. The file mode will be copied from the source and
 // the copied data is synced/flushed to stable storage.
-func CopyFile(src, dst string) (err error) {
+func CopyFile(src, dst string) error {
 	in, err := os.Open(src)
 	if err != nil {
-		return //nolint: nakedret
+		return err
 	}
 	defer in.Close()
 
 	out, err := os.Create(dst)
 	if err != nil {
-		return //nolint: nakedret
+		return err
 	}
 	defer func() {
 		if e := out.Close(); e != nil {
@@ -54,30 +54,30 @@ func CopyFile(src, dst string) (err error) {
 
 	_, err = io.Copy(out, in)
 	if err != nil {
-		return //nolint: nakedret
+		return err
 	}
 
 	err = out.Sync()
 	if err != nil {
-		return //nolint: nakedret
+		return err
 	}
 
 	si, err := os.Stat(src)
 	if err != nil {
-		return //nolint: nakedret
+		return err
 	}
 	err = os.Chmod(dst, si.Mode())
 	if err != nil {
-		return //nolint: nakedret
+		return err
 	}
 
-	return //nolint: nakedret
+	return err
 }
 
 // CopyDir recursively copies a directory tree, attempting to preserve permissions.
 // Source directory must exist. If destination already exists we'll clobber it.
 // Symlinks are ignored and skipped.
-func CopyDir(src string, dst string) (err error) {
+func CopyDir(src string, dst string) error {
 	src = filepath.Clean(src)
 	dst = filepath.Clean(dst)
 
@@ -91,7 +91,7 @@ func CopyDir(src string, dst string) (err error) {
 
 	_, err = os.Stat(dst)
 	if err != nil && !os.IsNotExist(err) {
-		return //nolint: nakedret
+		return err
 	}
 	if err == nil {
 		// it exists so let's remove it
@@ -102,12 +102,12 @@ func CopyDir(src string, dst string) (err error) {
 
 	err = os.MkdirAll(dst, si.Mode())
 	if err != nil {
-		return //nolint: nakedret
+		return err
 	}
 
 	entries, err := os.ReadDir(src)
 	if err != nil {
-		return //nolint: nakedret
+		return err
 	}
 
 	for _, entry := range entries {
@@ -117,13 +117,13 @@ func CopyDir(src string, dst string) (err error) {
 		if entry.IsDir() {
 			err = CopyDir(srcPath, dstPath)
 			if err != nil {
-				return //nolint: nakedret
+				return err
 			}
 		} else {
 			var info os.FileInfo
 			info, err = entry.Info()
 			if err != nil {
-				return //nolint: nakedret
+				return err
 			}
 
 			// Skip symlinks.
@@ -133,10 +133,10 @@ func CopyDir(src string, dst string) (err error) {
 
 			err = CopyFile(srcPath, dstPath)
 			if err != nil {
-				return //nolint: nakedret
+				return err
 			}
 		}
 	}
 
-	return //nolint: nakedret
+	return err
 }