First up, make sure that the Big Ass Textfile is stored in Git (you don’t want your life’s TODO list suddenly vanish).

Now that it’s in Git, feel free to delete each DONE task.

And finally, have a cron job that on the hour does something like ‘git diff > message.txt; git commit -F message.txt’

<— this way, you have your day’s TADA list AND your list in now searchable with dates via ‘git log’

(This was my TODO list for years until I declared TODO bankruptcy and have gone back to physical cards)