transaction: support for callbacks during abort...
transaction: support for callbacks during abort
Previous transaction work added callbacks to be called during regular
transaction commit/close. As part of refactoring Mozilla's pushlog
extension (an extension that opens a SQLite database and tries to tie
its transaction semantics to Mercurial's transaction), I discovered that
the new transaction APIs were insufficient to avoid monkeypatching
transaction instance internals. Adding a callback that is called during
transaction abort removes the necessity for monkeypatching and completes
the API.
