#+TITLE: Review History

The review history is stored in a tsv file, to avoid cluttering org
files. This makes it easy to calculate review statistics.

At first, I used an org drawer to store the review history but that
added to much overhead to the files (in one instance 6.5k lines of
review history for a file of 9.5k lines in total).

Columns:
1. Date in ISO8601 format, second precision
2. Filename
3. Card ID
4. Position
5. Ease (before review)
6. Box (before review)
7. Interval (before review)
8. Rating

More advanced review algorithms might need to use the review history
of a card. In this case, the card ID + position should be used to look
up the review history, as the filename can change when moving cards
from file to file.