Deploying GitLab pages for different branches

It is possible to keep several pages published for different pipelines/branches.

To do that you need to copy your pages content (basically test report, or whatever needs to be published) to specific unique directory in public folder. For example, the name of the directory can be the id of pipeline (CI_PIPELINE_ID). So the path to pages sources would be like public/$CI_PIPELINE_ID/.

Then the whole public folder should be defined as artifacts with specific unique name (here again "$CI_PIPELINE_ID" can be used).

Unique name for artifacts is needed to not override the artifacts with the next pipeline execution (if name is not specified, the default name will be taken https://docs.gitlab.com/ee/ci/yaml/#artifactsname).

Then you can access the published report via the link:

https://yourGitlab/yourNamespace/yourProjectName/{CI_PIPELINE_ID}/index.html

, that means you can access all your saved reports by changing the pipeline id.

My example:

stages:
  - publish

cache:
  # Required to keep artifacts from old builds, e.g. from master
  paths:
    - public

pages:
  stage: publish
  script:
    - mkdir -p public/$CI_PIPELINE_ID
    - cp target/site/allure-maven-plugin/* public/$CI_PIPELINE_ID/ -R
  artifacts:
    name: "$CI_PIPELINE_ID"
    paths:
      - public
    expire_in: 5 days
  when: always

I've had success using the browsable artifacts for this purpose. In your example, you would create a job for your develop branch and set the PUBLIC_URL to the path on gitlab.io where the job's artifacts are published:

develop:
    artifacts:
        paths:
          - public

    environment:
        name: Develop
        url: "https://$CI_PROJECT_NAMESPACE.gitlab.io/-/$CI_PROJECT_NAME/-/jobs/$CI_JOB_ID/artifacts/public/index.html"

    script: |
        # whatever

    stage: deploy

    variables:
        PUBLIC_URL: "/-/$CI_PROJECT_NAME/-/jobs/$CI_JOB_ID/artifacts/public"

Setting the environment as indicated produces a »Review app« link in relevant merge requests, allowing you to get to the artifacts with a single click.

Note: if your repository is in a subgroup, you need to insert the subgroup name in two places above above between /-/ and $CI_PROJECT_NAME for the resulting URLs to work.