如何在GIT中重新连接分离的HEAD

（我看到有很多与此有关的问题，但我还没有找到能解决我确切问题的方法）。

我正在运行gitlab-ci，当运行程序签出我的代码时，它作为分离的头部运行。这是在运行程序git status目录中运行命令时得到的信息。

git status
# HEAD detached at 847fe59
nothing to commit, working directory clean

对于我正在做的事情，我需要做的是将该头重新附加到我的开发分支，然后git pull在完整的存储库中使用，以在Docker容器中使用。我猜gitlab ci只签出最后一次提交以保存克隆完整的回购，这是可以理解的。

在我的.gitlab-ci.yml文件中，我尝试了以下操作...

- git checkout origin/$CI_BUILD_REF_NAME
- git pull

在控制台中提供以下输出...

    $ git checkout $CI_BUILD_REF_NAME
    Switched to a new branch 'develop'
    Branch develop set up to track remote branch develop from origin.
$ git pull
You are not currently on a branch. Please specify which
branch you want to merge with. See git-pull(1) for details.

Is there an easy way to reattach the head? Most of the solutions I've seen deal with the fact a change has been committed onto the detached head however this isn't the case for me. I just want to get my full develop branch in my docker container with all of my git history.

Or if there is a way to stop gitlab ci from checking out the detached head that would also be great.