sa-update-flag add public preview description to env BUILDKITE_PULL_REQUEST_USING_MERGE_REFSPEC

[SorchaAbel]

Description

Customers need to contact support to use this flag. Updating the description to reflect it's in private preview

Context

Changes

bootstrap.go

Testing

go run *.go bootstrap --help | grep -A2 "pull-request-using-merge-refspec"

Whether the agent should attempt to checkout the pull request commit using the merge refspec. This feature is in private preview and requires backend enablement—contact support to enable (default: false) [$BUILDKITE_PULL_REQUEST_USING_MERGE_REFSPEC]
  --agent value                        The name of the agent running the job [$BUILDKITE_AGENT_NAME]
  --queue value                        The name of the queue the agent belongs to, if tagged [$BUILDKITE_AGENT_META_DATA_QUEUE]

Disclosures / Credits

nothing to disclose