backup: fix gke wif with empty credential file

[Leavrth]

No description provided.

[Copilot]

Pull request overview

Updates the TiDB backup-manager container entrypoints to better support GKE Workload Identity Federation by avoiding creation/use of an empty GCP credentials file, allowing Google ADC to work correctly when no JSON key is provided.

Changes:

• Only create /tmp/google-credentials.json and set GOOGLE_APPLICATION_CREDENTIALS when GCS_SERVICE_ACCOUNT_JSON_KEY is provided.
• Omit service_account_file from rclone.conf unless a service account JSON key is provided.
• Unset GOOGLE_APPLICATION_CREDENTIALS when no service account JSON key is provided to avoid forcing an empty credentials file.

Reviewed changes

Copilot reviewed 2 out of 2 changed files in this pull request and generated no comments.

File	Description
images/tidb-backup-manager/entrypoint.sh	Conditionalize GCS credentials file creation and rclone GCS config to avoid empty credential file behavior.
images/tidb-backup-manager/e2e-entrypoint.sh	Mirrors the same conditional GCS credential handling for the E2E image entrypoint.

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[ti-chi-bot]

[APPROVALNOTIFIER] This PR is APPROVED

This pull-request has been approved by: liubog2008

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Details

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• OWNERS [liubog2008]

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[ti-chi-bot]

[LGTM Timeline notifier]

Timeline:

• 2026-05-12 03:50:02.886210286 +0000 UTC m=+151171.418989605: ☑️ agreed by liubog2008.

[liubog2008]

/hold

[Leavrth]

/retest

[liubog2008]

retest

[liubog2008]

/retest

[liubog2008]

/unhold

[Leavrth]

/cherry-pick release-1.6

[ti-chi-bot]

@Leavrth: new pull request created to branch release-1.6: #6893.

Details

In response to this:

/cherry-pick release-1.6

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