docs: add a changelog

The project kept no change history of its own, so the tags were the
only record of what each release contained.

- Summarise 2.0.0, 2.0.1 and 2.0.2 by what changed for the user.
- Link the changelog from the README.

CHANGELOG.md

@@ -0,0 +1,43 @@
+# Changelog
+
+All notable changes to this project will be documented in this file.
+
+## [2.0.2] - 2026-09-04
+
+### Added
+- Accepted `-e` as the short form of `download --exclude`.
+
+### Changed
+- Transferred files larger than the memory available, in both directions.
+- Left an existing local file intact when a download fails part way through.
+- Showed the reason the server gave when it refused a request.
+- Updated dependencies.
+
+### Fixed
+- Kept a session working across concurrent runs, long server queues, and providers that rotate refresh tokens.
+- Listed a tree containing locked folders with `ls --json --recursive` instead of failing on the first one.
+- Other minor fixes to `ls --json` output, remote path handling, and the login cache.
+
+### Security
+- Verified the downloaded archive against the release checksum before `selfupdate` replaces the binary.
+
+## [2.0.1] - 2026-06-12
+
+### Added
+- Accepted a DOI in place of a path, as `remote:10.xxxx/prefix.ID[/sub/path]`.
+- Allowed `download` and the read-only commands to run without signing in.
+
+## [2.0.0] - 2026-04-20
+
+First release of the command-line client.
+
+### Added
+- Commands `config`, `login`, `logout`, `whoami`, `labs`, `ls`, `mkdir`, `upload`, `download`, `mv`, `cp`, `rm`, `chacl`, `metadata`, `file-metadata`, `version`, and `selfupdate`.
+- Release build scripts for Linux, macOS, and Windows.
+
+### Changed
+- Sped up transfers by working on folders and files in parallel, bounded by `MDRS_CLIENT_CONCURRENT`.
+
+### Fixed
+- Kept the session valid throughout a long-running transfer, and across concurrent runs.
+- Handled file and folder names with combining characters consistently.

README.md

@@ -241,6 +241,10 @@ mdrs --help
 mdrs upload --help
 ```
 
+## Changelog
+
+See [CHANGELOG.md](./CHANGELOG.md) for the full change history.
+
 ## License
 
 [MIT](LICENSE) © 2026- Neuroinformatics Unit, RIKEN CBS