[JENKINS-45927] Truncate verbose CauseOfBlockage messages in queue

[stevearmstrong-dev]

See JENKINS-45927

Testing done

Added comprehensive unit tests in CompositeCauseOfBlockageTest:

• Few reasons (no truncation)
• Exactly 5 reasons (boundary case)
• More than 5 reasons (truncation)
• 100 reasons (extreme case, verifies length is reasonable)

Proposed changelog entries

• Truncate verbose queue blockage messages to show maximum 5 reasons with "... and N more" suffix.

Proposed upgrade guidelines

N/A

Submitter checklist

• The Jira issue, JENKINS-45927, is well-described.
• The changelog entries and upgrade guidelines are appropriate for the audience affected by the change (users or developers, depending on the change) and are in the imperative mood.
• There is automated testing or an explanation as to why this change has no tests.
• New public classes, methods, and fields are annotated with @Restricted or have @since TODO Javadoc.
• New deprecations are annotated with @Deprecated(since = "TODO").
• New or fixed UI is crresponsible to Content Security Policy defaults.
• If dependency changes, these were updated to link to relevant changelogs.
• If new extension/APIs were added, there is link to its consumers.

Desired reviewers

@timja

Before the changes are marked as ready-for-merge:

Maintainer checklist

• There are at least two (2) approvals for the pull request and no outstanding requests for change.
• Conversations in the pull request are over, or it is explicit that a reviewer is not blocking the change.
• Changelog entries in the pull request title and/or Proposed changelog entries are accurate, human-readable, and in the imperative mood.
• Proper changelog labels are set so that the changelog can be generated automatically.
• If the change needs additional upgrade steps from users, the upgrade-guide-needed label is set and there is a Proposed upgrade guidelines section in the pull request title (see example).
• If it would make sense to backport the change to LTS, a Jira issue must exist, be a Bug or Improvement, and be labeled as lts-candidate to be considered (see query).

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Summary

When hovering over queued build items, Jenkins displays extremely verbose blockage reasons that can fill the entire browser window. The message lists every node with format: "nodeA doesn't have label X; nodeB doesn't have label X; ..." for ALL nodes.

Changes

• Modified CompositeCauseOfBlockage.getShortDescription() to truncate messages when there are more than 5 reasons
• Shows first 5 reasons followed by "... and N more" to keep tooltips readable
• Added comprehensive unit tests for the truncation behavior

Before/After

Before: "node1 doesn't have label X; node2 doesn't have label X; node3 doesn't have label X; ... (continues for all 100 nodes)"

After: "node1 doesn't have label X; node2 doesn't have label X; node3 doesn't have label X; node4 doesn't have label X; node5 doesn't have label X; ... and 95 more"

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[timja]

Please restore (and follow) the PR template: https://github.com/jenkinsci/jenkins/blob/master/.github/PULL_REQUEST_TEMPLATE.md

[stevearmstrong-dev]

/label rfe

[stevearmstrong-dev]

Please restore (and follow) the PR template: https://github.com/jenkinsci/jenkins/blob/master/.github/PULL_REQUEST_TEMPLATE.md

Done.
Please review. @timja
Thanks

[MarkEWaite]

This PR is now ready for merge. We will merge it after the master branch is unlocked, if there is no negative feedback.

/label ready-for-merge

[MarkEWaite]

Tested in the plugin BOM to confirm that it is not breaking tests there. Pull request is:

• Test Truncate verbose CauseOfBlockage messages in queue bom#6034

Since this may affect the UI, needs to be tested in acceptance test harness.

[MarkEWaite]

Passed acceptance test harness.

[timja]

Could you provide some screenshots of what it looks like in the usecases you've provided?

[A1exKH]

LGTM.

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