專案目錄底下的 .git/config 檔案內，記錄有 Git 的 remote url，如果是 GitHub，長相類似這樣：
[remote "origin"]
url = [email protected]:akccakcctw/project.git
fetch = +refs/heads/*:refs/remotes/origin/*
只要在下面新增一行 fetch = +refs/pull/*/head:refs/remotes/origin/pr/*：
[remote "origin"]
url = [email protected]:akccakcctw/project.git
fetch = +refs/heads/*:refs/remotes/origin/*
fetch = +refs/pull/*/head:refs/remotes/origin/pr/*
使用 git fetch origin 時就可以 fetch 到 PR 的 branch：
$ git fetch origin
From github.com:akccakcctw/project
* [new ref] refs/pull/1000/head -> origin/pr/1000
* [new ref] refs/pull/1002/head -> origin/pr/1002
* [new ref] refs/pull/1004/head -> origin/pr/1004
* [new ref] refs/pull/1009/head -> origin/pr/1009
...
成功 fetch 後就能 checkout 到該 branch 了：
$ git checkout pr/1002
Branch pr/1002 set up to track remote branch pr/1002 from origin.
Switched to a new branch 'pr/1002'
同理，如果你是用 Gitlab，則把 pull 改為 merge-requests 即可：
[remote "origin"]
url = https://gitlab.com/akccakcctw/project.git
fetch = +refs/heads/*:refs/remotes/origin/*
fetch = +refs/merge-requests/*/head:refs/remotes/origin/pr/*