df7f1c2ead
Fix #31738 When pushing a new branch, the old commit is zero. Most git commands cannot recognize the zero commit id. To get the changed files in the push, we need to get the first diverge commit of this branch. In most situations, we could check commits one by one until one commit is contained by another branch. Then we will think that commit is the diverge point. And in a pre-receive hook, this will be more difficult because all commits haven't been merged and they actually stored in a temporary place by git. So we need to bring some envs to let git know the commit exist.
Git Module
This module is merged from https://github.com/go-gitea/git which is a Go module to access Git through shell commands. Now it's a part of gitea's main repository for easier pull request.