Add [ci-skip] for merge_request pipelines

Problem to solve

There are some cases where we don't want to waste build time for specific merge requests. Thus, if a MR description contains [ci skip] (or any other form, with _- or combined cases) we should be able to skip a job via only/except directives.

The same mechanism exists for regular pipelines (those not executed in a merge request context). However, in this case too one should have control if a job is executed or NOT via only/except directives that check CI_COMMIT_MESSAGE.

Intended users

Developers.

Further details

We currently hack this functionality in an ugly as hell pre-build check that looks like this:

  before_script:
    # skip build if MR description has [ci-skip]
    - "[Net.ServicePointManager]::SecurityProtocol = [Net.SecurityProtocolType]::Tls12"
    - $GLPT = @{ 'Private-Token' = $env:GitLab_PrivateToken }
    - $GITLAB_API  = 'https://git.DOMAIN.TLD/api/v4'
    - $GLMR_SINGLE = "$GITLAB_API/projects/1/merge_requests/$CI_MERGE_REQUEST_IID"
    - $mr = Invoke-RestMethod -headers $GLPT -uri $GLMR_SINGLE
    - if ($mr.description -match '\[ci[ _-]skip\]') { exit 0 }

I find it silly to ask for information that Gitlab can offer it directly.

Proposal

One simple solution would be to expose a CI_MERGE_REQUEST_DESCRIPTION variable like we have for TITLE (currently used for WIP check).

Another solution is have new variables passed for CI:

• CI_MERGE_REQUEST_SKIP*

Zero or more variables are created depending on the content of MR description:

• [ci skip] => CI_MERGE_REQUEST_SKIP (space or "_-" separator)
• [ci skip debug] => CI_MERGE_REQUEST_SKIP_DEBUG
• [ci skip release] => CI_MERGE_REQUEST_SKIP_RELEASE
• [ci skip anyalphanumstr] => CI_MERGE_REQUEST_SKIP_ANYALPHANUMSTR
• [ci skip any alphanum str] => CI_MERGE_REQUEST_SKIP_ANY_ALPHANUM_STR
• etc

Documentation

TODO

Testing

TODO