docs(changelog): add unreleased migration notes

changelog.md

@@ -7,6 +7,27 @@ and this project adheres to [Semantic Versioning](https://semver.org/spec/v2.0.0
 
 ## [Unreleased]
 
+### Added
+
+- Native Go implementations for `clone`, `link`, `unlink`, and `track`.
+- Containerized behavior test suite for command parity validation.
+- Dedicated test suites for `list`, `show_path`, `status`, `diff`, and `version`.
+- Just workflow support for building and running the Linux behavior binary.
+
+### Changed
+
+- CLI argument parsing migrated to Kong.
+- Git operations for clone and track migrated to `go-git`.
+- Release notes standardized to Keep a Changelog format.
+
+### Fixed
+
+- `status` and `diff` now consistently write through configured app output writers.
+
+### Removed
+
+- Legacy Ruby implementation and Ruby toolchain.
+
 ## [1.1.6] - 2017-12-20
 
 ### Fixed