## Objective
Implement absolute minimum viable product for the changes proposed in bevyengine/rfcs#53.
## Solution
- Remove public mutative access to `Parent` (Children is already publicly read-only). This includes public construction methods like `Copy`, `Clone`, and `Default`.
- Remove `PreviousParent`
- Remove `parent_update_system`
- Update all hierarchy related commands to immediately update both `Parent` and `Children` references.
## Remaining TODOs
- [ ] Update documentation for both `Parent` and `Children`. Discourage using `EntityCommands::remove`
- [x] Add `HierarchyEvent` to notify listeners of hierarchy updates. This is meant to replace listening on `PreviousParent`
## Followup
- These changes should be best moved to the hooks mentioned in #3742.
- Backing storage for both might be best moved to indexes mentioned in the same relations.
# Objective
Users often ask for help with rotations as they struggle with `Quat`s.
`Quat` is rather complex and has a ton of verbose methods.
## Solution
Add rotation helper methods to `Transform`.
Co-authored-by: devil-ira <justthecooldude@gmail.com>
# Objective
Reduce the catch-all grab-bag of functionality in bevy_core by minimally splitting off time functionality into bevy_time. Functionality like that provided by #3002 would increase the complexity of bevy_time, so this is a good candidate for pulling into its own unit.
A step in addressing #2931 and splitting bevy_core into more specific locations.
## Solution
Pull the time module of bevy_core into a new crate, bevy_time.
# Migration guide
- Time related types (e.g. `Time`, `Timer`, `Stopwatch`, `FixedTimestep`, etc.) should be imported from `bevy::time::*` rather than `bevy::core::*`.
- If you were adding `CorePlugin` manually, you'll also want to add `TimePlugin` from `bevy::time`.
- The `bevy::core::CorePlugin::Time` system label is replaced with `bevy::time::TimeSystem`.
Co-authored-by: Carter Anderson <mcanders1@gmail.com>
# Objective
- Small change that better facilitates custom animation systems
## Solution
- Added a public access function to `bevy::animation::AnimationClip`, making duration publicly readable
---
# Objective
- While playing with animated models, I noticed some were a little off
## Solution
- Some animations curves only have one keyframe, they are used to set a transform to a given value
- Those were ignored as we're never exactly at the ts 0.0 of an animation. going there explicitly (`.set_elapsed(0.0).pause()`) would crash
- Special case this as there isn't much to animate in this case
