transaction: allow registering a temporary transaction file During the transaction, files may be created to store or expose data involved in the transaction (eg: changelog index data are written in a 'changelog.i.a' for hooks). But we do not have an official way to record such file creation and make sure they are cleaned up. The lack of clean-up is currently okay because there is a single file involved and a single producer/consumer. However, as we want to expose more data (bookmarks, phases, obsmarker) we need something more solid. The 'backupentries' mechanism could handle that. Temporary files can be encoded as a backup of nothing '('', <temporarypath>)'. We "need" to attach it to the same mechanism as we use to be able to use temporary transaction files outside of .'store/' and 'backupentries' is expected to gain such feature. This changeset makes it clear that we should rename 'backupentries' to something more generic.

transaction: always generate file on close The conditionnal was buggy and file were only generated if "onclose" was defined. By luck, "onclose" was always defined.

remove: move most of the implementation into cmdutils.remove() This will allow access to the reusable parts from subrepos, similar to add(), forget(), etc.

revlog: increase I/O bound to 4x the amount of data consumed This doesn't affect normal clones since they'd be bound by the CPU bound below anyway -- it does, however, improve generaldelta clones significantly. This also results in better deltaing for generaldelta clones -- in generaldelta clones, we calculate deltas with respect to the closest base if it has a higher revision number than either parent. If the base is on a significantly different branch, this can result in pointlessly massive deltas. This reduces the number of bases and hence the number of bad deltas. Empirically, for a highly branchy repository, this resulted in an improvement of around 15% to manifest size.