Research adding support for savepoints

[simonw]

https://www.sqlite.org/lang_savepoint.html

Savepoints are like regular transactions except they have names and can be nested.

Would there be any value in adding support to them to sqlite-utils, potentially as some kind of context manager? Something like this:

with db.savepoint("name"):
    # do stuff
    with db.savepoint("name2"):
        # do more stuff
        raise Release # Rolls back to before "name2" savepoint

I've never used this feature so I'm not comfortable adding anything like this without a bunch of extra research.

[simonw]

Django makes extensive use of savepoints for nested transactions: https://docs.djangoproject.com/en/4.0/topics/db/transactions/#savepoints

[simonw]

Handled by db.atomic(): #757