BigQuery supports setting the if-match and if-none-match headers (see here) to check for etag match or mismatch when requesting some resource.

We should add support for etagMatch and etagNotMatch options. This support can be provided once the following issues are closed:

• Tables create does not return a complete Table resource #340
• Create and get dataset/table return the same resource but different etags #466
• Dataset.delete, Table.delete and Job.cancel ignore the if-non-match header #468