# Objective
Some sort calls and `Ord` impls are unnecessarily complex.
## Solution
Rewrite the "match on cmp, if equal do another cmp" as either a
comparison on tuples, or `Ordering::then_with`, depending on whether the
compare keys need construction.
`sort_by` -> `sort_by_key` when symmetrical. Do the same for
`min_by`/`max_by`.
Note that `total_cmp` can only work with `sort_by`, and not on tuples.
When sorting collected query results that contain
`Entity`/`MainEntity`/`RenderEntity` in their `QueryData`, with that
`Entity` in the sort key:
stable -> unstable sort (all queried entities are unique)
If key construction is not simple, switch to `sort_by_cached_key` when
possible.
Sorts that are only performed to discover the maximal element are
replaced by `max_by_key`.
Dedicated comparison functions and structs are removed where simple.
Derive `PartialOrd`/`Ord` when useful.
Misc. closure style inconsistencies.
## Testing
- Existing tests.
b78efd339d