Bug: Wrong upstream set

Steps to reproduce:

Preparation:

1. Fresh repo:

   git init
   git add -all
   git commit -a -m "Initial commit"
   git push --set-upstream https://gitlab.com/example_group/example_subgroup/example_project.git master

2. Create and switch to a new branch named beta tracking the current:

   git switch --track --create beta
   git push --set-upstream https://gitlab.com/example_group/example_subgroup/example_project.git beta

3. Same as above but this time the new branch is named alpha:

   git switch --track --create alpha 
   git push --set-upstream https://gitlab.com/example_group/example_subgroup/example_project.git alpha

4. Browse to the project on GitLab.
5. Create an issue.
6. Create a merge request using that issue, and select the alpha branch as source branch.

I have already done the above at @trimoon-inc/system/archiso_setup 😉 https://gitlab.com/trimoon-inc/system/archiso_setup

The bug:

1. Pull the project on your machine to get the updates.

   git pull

2. Grab that merge request using your util.

   git mr 1

3. Check the configured merge value in your cloned repo of this new branch.
   If you cloned the repo I prepared, it will show refs/heads/1-improve-alpha-version\nHEAD\nalpha\nbeta\nmaster which is wrong 😉
4. It should be refs/heads/1-improve-alpha-version
   Note the \nHEAD\nalpha\nbeta\nmaster at end of the wrong value 👍

Evidence of bad value:

You won't be able to check the status of the branch relative to the upstream using git status