Automatic merge from submit-queue (batch tested with PRs 53694, 53919). If you want to cherry-pick this change to another branch, please follow the instructions <a href="https://github.com/kubernetes/community/blob/master/contributors/devel/cherry-picks.md">here</a>.
Do not crash when groupVersion doesn't have a group
**What this PR does / why we need it**: fixes a crash when the group is empty, because it assumes that split will return a two element array. Which it doesn't.
**Which issue this PR fixes** *(optional, in `fixes #<issue number>(, fixes #<issue_number>, ...)` format, will close that issue when PR gets merged)*: fixeskubernetes/kubectl#78
**Special notes for your reviewer**:
**Release note**:
```release-note
NONE
```
Major changes:
- Don't generate a patch, instead generate the merged object so it can be used with PUT
- Separate tree parsing logic to collate items in a list from the delete / merge / replace / add logic when merging
- Use openapi for merge strategy metadata so it works with extensions and version skew
- Support multi-field mergekeys when merging lists
- Support replace strategy for maps
- Reduce complexity of generating order when merging lists - keep the locally defined order and append remote only-items
Continue to support:
- Explicitly setting fields to null
- Merging lists of primitives
- Don't randomize ordering when merging lists
TODO:
- Retain keys
- Conflict detection
xichengliudui