chore: simplify CopyDir

Use the standard library function [`os.CopyFS`](https://pkg.go.dev/os#CopyFS) to copy directories.
This also should be slightly faster.

models/unittest/fscopy.go

@@ -4,99 +4,12 @@
 package unittest
 
 import (
-	"errors"
-	"io"
 	"os"
-	"path"
-	"strings"
-
-	"code.gitea.io/gitea/modules/util"
 )
 
-// Copy copies file from source to target path.
-func Copy(src, dest string) error {
-	// Gather file information to set back later.
-	si, err := os.Lstat(src)
-	if err != nil {
-		return err
-	}
-
-	// Handle symbolic link.
-	if si.Mode()&os.ModeSymlink != 0 {
-		target, err := os.Readlink(src)
-		if err != nil {
-			return err
-		}
-		// NOTE: os.Chmod and os.Chtimes don't recognize symbolic link,
-		// which will lead "no such file or directory" error.
-		return os.Symlink(target, dest)
-	}
-
-	sr, err := os.Open(src)
-	if err != nil {
-		return err
-	}
-	defer sr.Close()
-
-	dw, err := os.Create(dest)
-	if err != nil {
-		return err
-	}
-	defer dw.Close()
-
-	if _, err = io.Copy(dw, sr); err != nil {
-		return err
-	}
-
-	// Set back file information.
-	if err = os.Chtimes(dest, si.ModTime(), si.ModTime()); err != nil {
-		return err
-	}
-	return os.Chmod(dest, si.Mode())
-}
-
 // CopyDir copy files recursively from source to target directory.
 //
-// The filter accepts a function that process the path info.
-// and should return true for need to filter.
-//
 // It returns error when error occurs in underlying functions.
-func CopyDir(srcPath, destPath string, filters ...func(filePath string) bool) error {
-	// Check if target directory exists.
-	if _, err := os.Stat(destPath); !errors.Is(err, os.ErrNotExist) {
-		return util.NewAlreadyExistErrorf("file or directory already exists: %s", destPath)
-	}
-
-	err := os.MkdirAll(destPath, os.ModePerm)
-	if err != nil {
-		return err
-	}
-
-	// Gather directory info.
-	infos, err := util.StatDir(srcPath, true)
-	if err != nil {
-		return err
-	}
-
-	var filter func(filePath string) bool
-	if len(filters) > 0 {
-		filter = filters[0]
-	}
-
-	for _, info := range infos {
-		if filter != nil && filter(info) {
-			continue
-		}
-
-		curPath := path.Join(destPath, info)
-		if strings.HasSuffix(info, "/") {
-			err = os.MkdirAll(curPath, os.ModePerm)
-		} else {
-			err = Copy(path.Join(srcPath, info), curPath)
-		}
-		if err != nil {
-			return err
-		}
-	}
-	return nil
+func CopyDir(srcPath, destPath string) error {
+	return os.CopyFS(destPath, os.DirFS(srcPath))
 }