revert: add more padding in the dispatch list We are going to add more sets and some of them will have longer names. We add padding in a standalone patch for readbility purposes.

revert: add documentation in the dispatch table More sets are coming so documenting the existing ones will help.

revert: add a way for external extensions to prefetch file data This allow extensions that mess with the storage layer (remotefilelog, largefile) to prefetch any data that will be accessed during the revert operation. We are currently fetching more data than theoretically required because the backup code is a bit stupid. Future patches will improve that.

merge with stable