In Heroku I can set up dev > staging > prod pipeline, and i.e. when tester says it is ready to get to staging, he moves commit from dev to staing with pressing "Promote". Is it available in GitLab?
So withouth touching git, just move a branch forward.
You can set the pipeline up in full with deployment to each environment, but set the release to require manual intervention using when
e.g.
deploy to dev
stage: dev_test
script:
- deploy...
when: manual
deploy to staging
stage: staging_release
script:
- deploy...
needs:
- deploy to dev
when: manual
The deployment will need to be manually triggered from the pipeline screen before it will take place