Rename before=[] and after=[]

[andsens]

The task properties before and after are really confusing. The description of these properties would be.

before describes which tasks the task at hand should run before, while after describes the ones it should run after.

However, one could also write the opposite, and it would still make sense (though being completely wrong).

before describes tasks that should run before the task at hand, while after describes the ones that should run after it.

Point is, the property names do not clarify anything, they actually just make it confusing. Additionally the before is currently place over the after line, instead the task order should be reflected in the reading order.

We could use run_after and run_before, but the essential problem is that the words describe the relation between the task at hand and the tasks in the lists instead of describing what the tasks in the lists are. I think predecessors and successors are a better fit. The MapPartitions would then look like this.

class MapPartitions(Task):
        description = 'Mapping volume partitions'
        phase = phases.volume_preparation
        predecessors = [PartitionVolume]
        successors = [filesystem.Format]

        def run(self, info):
                info.volume.partition_map.map(info.volume)