Preview the semantic release notes that would result from merging a Github PR.

This semantic-release plugin will post a Github PR comment with a preview of the release that would result from merging.

npm install -D semantic-release semantic-release-github-pr

npx semantic-release-github-pr

It helps to think about semantic-release-github-pr as a variation on semantic-release's default behavior, using the latter's plugin system to modify some behaviors:

• If a new release would result from running semantic-release, instead of publishing a new release of a package, it posts a comment with the changelog to matching Github PRs.

• It posts a static message when there's no release (for clarity).

• It cleans up any PR comments it previously made (to keep from flooding PRs or leaving outdated information).

A PR gets a comment if:

1. The PR's from branch matches the current branch (that this plugin is being run on).

   To cover multiple CI scenarios (see below), either of:

   1. The PR's test merge commit matches the current branch's git HEAD.
   2. The PR and the current branch have the same git HEAD.

2. The PR's base branch matches master (default) unless otherwise configured via the baseBranch option.

It is assumed the user is already fully familiar with semantic-release and its workflow.

Github authentication must be configured, exactly the same as for semantic-relase's default @semantic-release/github plugin. PR comments will be posted by the associated GitHub user.

It's possible to configure the expected base branch when matching a PR via a baseBranch option set in the release config.

E.g., in a package.json release config:

{
  "release": {
    "baseBranch": "staging"
  }
}

This plugin is best used with a CI build process to fully automate the posting of comments in Github PRs. Ideally, it should run whenever a PR is opened/updated.

This plugin relies on semantic-release's dry-run feature. Unfortunately, that feature is gated by strict run-time checks, including one that ensures that the branch semantic-release runs on is in the release configuration. It depends on env-ci to enforce the checks in CI environments, which doesn't properly resolve the branch name when running in GitHub Actions, requiring a workaround:

    - run: git checkout -b ${{ github.head_ref }}
    - run: unset GITHUB_ACTIONS && npx semantic-release-github-pr

To only run when necessary, we use the $TRAVIS_PULL_REQUEST environment variable to detect whether the build is a "pull request build".

after_success:
  - "[[ $TRAVIS_PULL_REQUEST != 'false' ]] && npx semantic-release-github-pr || exit 0"

To run only when necessary, we use the $CI_PULL_REQUEST environment variable to detect whether the build has a corresponding pull request.

Unfortunately, CircleCI only supports building on push, not when a PR is created. This limits the usefulness of the plugin somewhat, as a build will have to be triggered manually after a PR is opened for the changelog to post.

post:
  - "[[ $CI_PULL_REQUEST != '' ]] && npx semantic-release-github-pr || exit 0"