Fix scheduled pipeline

What does this MR do?

Fix scheduled pipeline

The scheduled pipeline failed with:

'ui:screenshot_collector' job needs 'ui:visual 1/2' job, but 'ui:visual 1/2' does not exist in the pipeline. This might be because of the only, except, or rules keywords. To need a job that sometimes does not exist in the pipeline, use needs:optional. 'ui:screenshot_collector' job needs 'ui:visual 2/2' job, but 'ui:visual 2/2' does not exist in the pipeline. This might be because of the only, except, or rules keywords. To need a job that sometimes does not exist in the pipeline, use needs:optional.

Which means the packages/gitlab-ui/.gitlab-ci.yml file was incorrectly included.

Though the is-default-branch condition added in !5838 (merged) evaluates to false if the pipeline source is schedule, that just means the next rule is checked. See https://docs.gitlab.com/ci/yaml/#rulesif.

The last rule only specifies changes, which:

when there is no Git push event, rules: changes always evaluates to true and the job always runs

So, these packages/*/.gitlab-ci.yml files were always being included in scheduled pipelines.

The fix is to explicitly exclude them with when: never.

This also adds if to the changes rule, to make it explicitly only for merge request events (merge requests, merge trains).

Screenshots or screen recordings

Integrations

• GitLab: mr_url
• CustomersDot: mr_url
• Duo UI: mr_url
• Status Page: mr_url
• Docs: mr_url
• Switchboard: mr_url

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