message: More documentation on bq upload script
diff: '''
  Script to process debug SGFs for upload to BigQuery.
  +
  +Handles one generation per invocation, for easy sharding of work.
  +
  +Usage:
  +python oneoffs/prepare_bigquery.py 000017-generation-number
  +
  +
  The load commands look like:
  bq load --project_id=$PROJECT_ID \
  --source_format=NEWLINE_DELIMITED_JSON \
  