Removed superfluous code now that connections use autocommit by default.
Deprecated transaction.commit/rollback_unless_managed.

Since "unless managed" now means "if database-level autocommit",
committing or rolling back doesn't have any effect.

Restored transactional integrity in a few places that relied on
automatically-started transactions with a transitory API.
Deprecated transaction.is_managed().

It's synchronized with the autocommit flag.
Moved standard SQL for savepoints in the base backend.

These methods are only called when uses_savepoints = True anyway.
Refactored implementation of savepoints.

Prepared for using savepoints within transactions in autocommit mode.
Added support for savepoints in SQLite.

Technically speaking they aren't usable yet.
Implemented an 'atomic' decorator and context manager.

Currently it only works in autocommit mode.

Based on @xact by Christophe Pettus.
Added some assertions to enforce the atomicity of atomic.
Deprecated the old transaction management APIs.
Made transaction management work even before the first SQL query.

Thanks Florian again.
Implemented atomic_if_autocommit.

It disables transaction management entirely when AUTOCOMMIT is False.
Deprecated TransactionMiddleware and TRANSACTIONS_MANAGED.

Replaced them with per-database options, for proper multi-db support.

Also toned down the recommendation to tie transactions to HTTP requests.
Thanks Jeremy for sharing his experience.
Re-ordered functions by deprecation status.
Updated the documentation for savepoints.

Apparently django.db.transaction used to be an object.
Added an explanation of transactions and grouped low-level APIs.
Added a note about long-running processes.

There isn't much else to say, really.
Added an option to disable the creation of savepoints in atomic.
Added a safety net for developers messing with autocommit.
Updated a test that doesn't make sense with autocommit.
Removed a test that no longer makes any sense.

Since unmanaged == autocommit, there's nothing to commit or roll back.