Move some functions to gitrepo package (#35543)

Refactor Git command functions to use WithXXX methods instead of
exposing RunOpts.
This change simplifies reuse across gitrepo and improves consistency,
encapsulation, and maintainability of command options.

---------

Co-authored-by: wxiaoguang <wxiaoguang@gmail.com>

modules/gitrepo/size.go

@@ -0,0 +1,37 @@
+// Copyright 2025 The Gitea Authors. All rights reserved.
+// SPDX-License-Identifier: MIT
+
+package gitrepo
+
+import (
+	"os"
+	"path/filepath"
+)
+
+const notRegularFileMode = os.ModeSymlink | os.ModeNamedPipe | os.ModeSocket | os.ModeDevice | os.ModeCharDevice | os.ModeIrregular
+
+// CalcRepositorySize returns the disk consumption for a given path
+func CalcRepositorySize(repo Repository) (int64, error) {
+	var size int64
+	err := filepath.WalkDir(repoPath(repo), func(_ string, entry os.DirEntry, err error) error {
+		if os.IsNotExist(err) { // ignore the error because some files (like temp/lock file) may be deleted during traversing.
+			return nil
+		} else if err != nil {
+			return err
+		}
+		if entry.IsDir() {
+			return nil
+		}
+		info, err := entry.Info()
+		if os.IsNotExist(err) { // ignore the error as above
+			return nil
+		} else if err != nil {
+			return err
+		}
+		if (info.Mode() & notRegularFileMode) == 0 {
+			size += info.Size()
+		}
+		return nil
+	})
+	return size, err
+}