Release procedure

This document describes how to release a new version.

Versioning

Follow semantic versioning 2.0.0 to choose the new version number.

Prepare change log entries

Add notable changes since the last release to CHANGELOG.md. It should look like:

(snip)
## [Unreleased]

### Added
- Implement ... (#35)

### Changed
- Fix a bug in ... (#33)

### Removed
- Deprecated `-option` is removed ... (#39)

(snip)

Bump version

1. Determine a new version number. Then set VERSION variable.

   # Set VERSION and confirm it. It should not have "v" prefix.
   $ VERSION=x.y.z
   $ echo $VERSION
   

2. Make a branch to release

   $ git neco dev "bump-$VERSION"
   

3. Edit CHANGELOG.md for the new version (example).

4. Commit the change and push it.

   $ git commit -a -m "Bump version to $VERSION"
   $ git neco review
   

5. Merge this branch.

6. Add a git tag to the main HEAD, then push it.

   # Set VERSION again.
   $ VERSION=x.y.z
   $ echo $VERSION
   
   $ git checkout main
   $ git pull
   $ git tag -a -m "Release v$VERSION" "v$VERSION"
   
   # Make sure the release tag exists.
   $ git tag -ln | grep $VERSION
   
   $ git push origin "v$VERSION"
   

GitHub actions will build and push artifacts such as container images and create a new GitHub release.