Move git config/remote to gitrepo package and add global lock to resolve possible conflict when updating repository git config file (#35151)

Partially fix #32018 

`git config` and `git remote` write operations create a temporary file
named `config.lock`. Since these operations are not atomic, they must
not be run in parallel. If two requests attempt to modify the same
repository concurrently—such as during a compare operation—one may fail
due to the presence of an existing `config.lock` file.

In cases where `config.lock` is left behind due to an unexpected program
exit, a global lock mechanism could allow us to safely remove the stale
lock file when a related error is detected. While this behavior is not
yet implemented in this PR, it is planned for a future enhancement.

---------

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

modules/gitrepo/config.go

@@ -0,0 +1,48 @@
+// Copyright 2025 The Gitea Authors. All rights reserved.
+// SPDX-License-Identifier: MIT
+
+package gitrepo
+
+import (
+	"context"
+	"strings"
+
+	"code.gitea.io/gitea/modules/git"
+	"code.gitea.io/gitea/modules/globallock"
+)
+
+func GitConfigGet(ctx context.Context, repo Repository, key string) (string, error) {
+	result, _, err := git.NewCommand("config", "--get").
+		AddDynamicArguments(key).
+		RunStdString(ctx, &git.RunOpts{Dir: repoPath(repo)})
+	if err != nil {
+		return "", err
+	}
+	return strings.TrimSpace(result), nil
+}
+
+func getRepoConfigLockKey(repoStoragePath string) string {
+	return "repo-config:" + repoStoragePath
+}
+
+// GitConfigAdd add a git configuration key to a specific value for the given repository.
+func GitConfigAdd(ctx context.Context, repo Repository, key, value string) error {
+	return globallock.LockAndDo(ctx, getRepoConfigLockKey(repo.RelativePath()), func(ctx context.Context) error {
+		_, _, err := git.NewCommand("config", "--add").
+			AddDynamicArguments(key, value).
+			RunStdString(ctx, &git.RunOpts{Dir: repoPath(repo)})
+		return err
+	})
+}
+
+// GitConfigSet updates a git configuration key to a specific value for the given repository.
+// If the key does not exist, it will be created.
+// If the key exists, it will be updated to the new value.
+func GitConfigSet(ctx context.Context, repo Repository, key, value string) error {
+	return globallock.LockAndDo(ctx, getRepoConfigLockKey(repo.RelativePath()), func(ctx context.Context) error {
+		_, _, err := git.NewCommand("config").
+			AddDynamicArguments(key, value).
+			RunStdString(ctx, &git.RunOpts{Dir: repoPath(repo)})
+		return err
+	})
+}