narrow: enforce that narrow spec is written within a transaction

narrow: write the narrow spec in a transaction during share It will be simpler if all write happens within transaction.

narrow: open the transaction sooner when unbundling That way, the narrow spec changes will be done within a transaction.

narrow: write the narrow spec in a transaction during clone It will be simpler if all write happens within transaction.

narrow: drop the dedicated backup code Now that the transaction manage the writes, we can simply use the transaction for backup. Some extra cleanup to ensure all changes happens within a transaction will be made in the next changesets.

narrow: delegate the dirstate's narrow spec writing to the transaction This make it more transactional and will help us to simplify their backup. The implementation is not great, but it keep the patch simple as this is not the time for a larger refactoring yet.

narrow: delegate the narrow spec writing to the transaction This make it more transactional and will help us to simplify their backup. The implementation is not great, but it keep the patch simple as this is not the time for a larger refactoring yet.

narrow: get the narrow patterns from the repository object instead of disk Relying on disk data make the transactionally of this change complicated, so let us start reading data from other API instead.

narrow: widden the lock context in `tracking` The tracking configuration we modify must be read under lock. So we grab the lock sooner.

narrow: move `only_show` handling sooner in `tracked` This will help us to improve the locking scope in the `tracked` command.