Merge requests like gitlab is naming them or pull requests like github is naming them are a great feature in my opinion. They summarize the changes done, to reach a dedicated goal and enable us to discuss and share the changes done. But what if you or somebody else forgot to create a merge request for your development branch? Or you run GitOps and need to promote your environment through different branches, do you want to create and merge manually?

There is a solution for this challenge, the merge request can be created via you CI in this case via Gitlab-CI.

Preparation

To start we need to prepare the repository. A GitLab access token with api access permission and the role necessary, mostly developer, to create the merge request, is needed. This token then needs to be available in GitLab CI variable which can be easiest done with glab. The name of the variable is MR_TOKEN, the token itself has to be pasted into the command.

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glab variable set MR_TOKEN <Put your token here>  -m

Alternative the ci variable can be set via the UI. Both option shall end with a picture similar to the this one.

CI Variable in Gitlab CI If you use the environment feature of gitlab adapt the environment parameter of the CI variable.

The CI job

After we have the CI variable MR_TOKEN we can utilize it in a CI job. For the purpose of this CI-Job I use the gitlab cli glab, which make it very easy to interact with the gitlab API via command line or CI-job. Beside the binary itself the project also provides a container image which we use here, see line 3. The container start with a glab entrypoint which we need to overwrite to execute a script within the CI-job. Within the script block the git repository needs to be configured, this is necessary for glab to work. Then it is straight forward, authentication with glab to the gitlab api while using the MR_TOKEN variable and the glab command similar to one you can execute on your local shell, to create merge request.

That is it!

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create_mr:
  image: 
    name: gitlab/glab:v1.33.0
    entrypoint: [""]
  stage: create_mr
  only:
    - schedules
  except:
    - main
  script:
    - git remote set-url origin "https://update-bot:${MR_TOKEN}@${CI_SERVER_HOST}/${CI_PROJECT_PATH}.git"
    - git fetch --all
    - git checkout $CI_COMMIT_REF_NAME
    - glab auth login --hostname gitlab.com --token "${MR_TOKEN}"
    - glab mr create 
      --fill 
      --label bot 
      --target-branch main 
      --yes

The code be found on https://gitlab.com/tiflor/auto_mr_creation_demo/.

embedding it into .gitlab-ci.yml

I like to have my jobs in dedicate files. That then needs to be included into the .gitlab-ci.yml, which can be done in the following way.

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include:
  - local: 'gitlab-ci/create_mr.yml'

stages:
  - create_mr

The job also need to run in a dedicated stage which is named create_mr.