This is the first of several commits that will modernize the beets codebase for
Python 2.6 conventions. (Compatibility with Python 2.5 is hereby abandoned.)
This commit makes rewrite explicitely match items using the .lower() function
instead of using Pythons builtin re.I flag.
This is required as the re.I flag only allows for case-independent pattern
matching with ascii chars. Even worse, the pattern is stored in lowercase when
using re.I, but the value to be matched isn't lowercased.
Example:
[rewrite]
artist Сергей Васильевич Рахманинов: Sergei Rachmaninoff
In an attempt to finally address the longstanding SQLite locking issues, I'm
introducing a way to explicitly, lexically scope transactions. The Transaction
class is a context manager that always fully fetches after SELECTs and
automatically commits on exit. No direct access to the library is allowed, so
all changes will eventually be committed and all queries will be completed. This
will also provide a debugging mechanism to show where concurrent transactions
are beginning and ending.
To support composition (transaction reentrancy), an internal, per-Library stack
of transactions is maintained. Commits only happen when the outermost
transaction exits. This means that, while it's possible to introduce atomicity
bugs by invoking Library methods outside of a transaction, you can conveniently
call them *without* a currently-active transaction to get a single atomic
action.
Note that this "transaction stack" concepts assumes a single Library object per
thread. Because we need to duplicate Library objects for concurrent access due
to sqlite3 limitation already, this is fine for now. Later, the interface should
provide one transaction stack per thread for shared Library objects.
The substitute() function now tries to use a pre-compiled template first. If
this raises an exception, it falls back to the slow path (interpretation).
