export historical metrics

when we are avle to collec metrics (#274), we should also have a task or option which exports the metrics with date stamp for all past commits

Start by reading issue #274 and the existing metrics collection work it describes. Identify where metrics are collected, then determine how a task or option could process all past commits and attach date stamps to exported results. Done means historical metrics can be exported for every past commit; no files or tests are named in this issue.

Written by the indexing model from the issue text.