Cannot choose which version of gitlab to run when using docker

Hi,

I'm using gitlab-ce via docker since a while. But I cannot choose which version to run. Today, I have run a git pull and I see a branche named 7.13.1, which I checked out. Then, I built the image and started it. But I'm still with 7.12.2. How can I force 7.13.1 when building an image?

Thanks.