Tasks: Really smart sort respecting subtasks

[TauPan]

I use both task deadlines and manual ordering with subtasks, sometimes both (see #503 for a related feature request).

Currently subtasks are lost in the smart sort order. So it would help me if the behaviour would change to respect the following constraints (in order of priority):

1. Subtask- (or Child-Parent-) relation between tasks is always respected, no matter what. (Parents and their children should never be separated.)
2. The current smart ordering algorithm sorts the items on the same hierarchical level within the same "family" (sibling tasks).
3. If there's a tie in the smart sorting order between siblings, the manual order is respected (i.e. only if the tasks have the same deadline '''and''' priority. (Similar to #449)

I hope this was coherent enough. For my personal preference, it would suffice if '''either''' #503 '''or''' this ticket would be implemented. I think #449 describes a subset of my requirements.

[abaker]

I would like to display subtasks properly in all sort modes so I plan on looking in to this

[pepedelosbosques]

+1

[HellAime]

+1

[TauPan]

It's been a long time and I have to add that nowadays I don't use smart sort any more, but sort by due date always. This does most of what I need, preferring urgency over importance, except respecting subtasks.

However I'm not sure what's the due date of a subtask. If it has none of its own, the due date of the parent task can be used (so it can be sorted underneath it) and if it has its own date, the subtask association must be broken (otherwise the order won't be correct).

[abaker]

Next release includes support for subtasks in all sort modes