revset: use '%' as an operator for 'only' With this patch, we can make it much easier to specify 'only(A,B)' -> A%B. Similarly, 'only(A)' -> A%. On Windows, '%' is a semi-reserved symbol in the following way: using non-bash shells (e.g. cmd.exe but NOT PowerShell, ConEmu, and cmder), %var% is only expanded when 'var' exists and is surrounded by '%'. That only leaves batch scripts which could prove to be problematic. I posit that this isn't a big issue because any developer of batch scripts already knows that to use '%' one needs to escape it by using a double '%%'. Alternatives to '%' could be '=' but that might be limiting our future if we ever decide to use temporary assignments in a revset.

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.