Currently, 3 options are implemented:
- options.prune (defaults to `false`) - Remove null or undefined
fields from the object after merging.
- options.merge (defaults to `true`) deep-merge nested fields, note
that dependency fields are always deep merged regardless of this option.
- options.warnIncompatibleVersions (defaults to `true`) Output warning
if two dependency version ranges don't intersect.
Closes#4779
* refactor: extract deps & config logic to separate files
* feat: implement a migrator to upgrade to eslint 6
* fix: add required deps for eslint v4
* test: move migrator tests to each standalone plugins
* refactor: use spread operator instead of Object.assign
EzioShiki