Pipelines for merge requests
Introduced in GitLab 11.6.
Usually, when you create a new merge request, a pipeline runs on the new change and checks if it's qualified to be merged into a target branch. This pipeline should contain only necessary jobs for checking the new changes. For example, unit tests, lint checks, and Review Apps are often used in this cycle.
With pipelines for merge requests, you can design a specific pipeline structure
for merge requests. All you need to do is just adding
only: [merge_requests] to
the jobs that you want it to run for only merge requests.
Every time, when developers create or update merge requests, a pipeline runs on
their new commits at every push to GitLab.
NOTE: Note: If you use both this feature and Merge When Pipeline Succeeds, pipelines for merge requests take precedence over the other regular pipelines.
For example, consider the following
build: stage: build script: ./build only: - branches - tags - merge_requests test: stage: test script: ./test only: - merge_requests deploy: stage: deploy script: ./deploy
After the merge request is updated with new commits, GitLab detects that changes
have occurred and creates a new pipeline for the merge request.
The pipeline fetches the latest code from the source branch and run tests against it.
In the above example, the pipeline contains only
deploy job doesn't have the
only: [merge_requests] rule,
deployment jobs will not happen in the merge request.
Pipelines tagged as merge request indicate that they were triggered when a merge request was created or updated.
The same tag is shown on the pipeline's details:
Excluding certain jobs
The behavior of the
only: merge_requests rule is such that only jobs with
that rule are run in the context of a merge request; no other jobs will be run.
However, you may want to reverse this behaviour, having all of your jobs to run except
for one or two. Consider the following pipeline, with jobs
C. If you want
all pipelines to always run
B, but only want
C to run for a merge request,
you can configure your
.gitlab-ci.yml file as follows:
.only-default: &only-default only: - master - merge_requests - tags A: <<: *only-default script: - ... B: <<: *only-default script: - ... C: script: - ... only: - merge_requests
B are getting the
only: rule to execute in all cases, they will
C specifies that it should only run for merge requests, so for any
pipeline except a merge request pipeline, it will not run.
As you can see, this will help you avoid a lot of boilerplate where you'd need
to add that
only: rule to all of your jobs in order to make them always run. You
can use this for scenarios like having only pipelines with merge requests get a
Review App set up, helping to save resources.
Important notes about merge requests from forked projects
Note that the current behavior is subject to change. In the usual contribution flow, external contributors follow the following steps:
- Fork a parent project.
- Create a merge request from the forked project that targets the
masterbranch in the parent project.
- A pipeline runs on the merge request.
- A maintainer from the parent project checks the pipeline result, and merge into a target branch if the latest pipeline has passed.
Currently, those pipelines are created in a forked project, not in the parent project. This means you cannot completely trust the pipeline result, because, technically, external contributors can disguise their pipeline results by tweaking their GitLab Runner in the forked project.
There are multiple reasons about why GitLab doesn't allow those pipelines to be
created in the parent project, but one of the biggest reasons is security concern.
External users could steal secret variables from the parent project by modifying
.gitlab-ci.yml, which could be some sort of credentials. This should not happen.
We're discussing a secure solution of running pipelines for merge requests that submitted from forked projects, see the issue about the permission extension.