Experiments history

[bpiwowar]

Instead of just keeping the last experiment, it would be better to keep the full history and be able to manage it:

• experiments history XP_ID would give the history
• experiments history-prune XP_ID TIMESTAMP_END TIMESTAMP_START would prune experiments between two timestamps (last-N could be a valid timestamp)
• experiments tag XP_ID TIMESTAMP TAGNAME to tag the experiment
• etc.