* hotfix: return error instead of log at `FromMapAndOption`
* chore: show error message
* hotfix: use correct function
* hotix: use `t.Helper()` and fix `t *testing.T order
* hotfix: wrapt the error of `FromMapAndOption`
* hotfix: meaningful message for an error
* hotfix: summarize in one line
* hotfix: fix the abandoned error and show meaningful message
* hotfix: start with helper function
* Keep TODO comment
* WIP
* Fix merge corner cases
* Add test for explicit !!merge tag
* Fix tests
* Cleanup
* Cleanup
* Fix deanchoring lists
* Add test case for keeping comments
* Add MapEntrySetter and fix json marshalling after deanchoring
* Keep duplicated keys
* Move MergeTag definition to yaml alias
* Remove go-spew from api
* Add support for sequence nodes on merge tags
* Add docstring to MapEntrySetter.Key
* Add docstring to MapEntrySetter struct
* Add tests to MapEntrySetter
* Fix duplicate merge key
* Revert whitespace changes on forked go-yaml
* Remove AssocMapEntry function
* Refactoring merge order
* Return errors on VisitFields and PipeE
* Add tests for each non-conforming map merges
The implementations in WNode are supposed to be thin,
as it will be removed once #2506 closes.
The change also makes some addjustments for the
upcoming flip of the enable_kyaml flag, pointing to
issue #3271.
