github-release.yml

name: GitHub Release

# Creates (or updates) the GitHub Release for a vX.Y.Z tag, with the release
# notes generated by GitHub from the PRs merged since the previous tag.
# `.github/release.yml` controls how those notes are grouped.
#
# Three entry points, one implementation:
#
#   workflow_call  -- how the automated flow gets here.  release.yml pushes the
#                     tag with GITHUB_TOKEN, and a tag pushed by GITHUB_TOKEN
#                     does NOT trigger another workflow, so release.yml calls
#                     this one directly instead of relying on the tag push.
#   push (tags)    -- for a tag pushed by hand
#                     (`git tag v0.3.35 && git push origin v0.3.35`).
#   workflow_dispatch -- to back-fill the Release for a tag that already exists.
#
# Only one of these fires per tag in practice; if two ever did,
# action-gh-release updates the existing Release rather than failing.

on:
  push:
    tags:
      - 'v*'
  workflow_call:
    inputs:
      tag:
        description: 'Tag to release, including the leading v'
        required: true
        type: string
  workflow_dispatch:
    inputs:
      tag:
        description: 'Tag to release, including the leading v (e.g. v0.3.35)'
        required: true
        type: string

permissions:
  contents: write

jobs:
  github-release:
    name: Publish GitHub Release
    runs-on: ubuntu-latest
    steps:
      # `inputs` is empty on a push event, so this falls back to the pushed tag.
      - name: Resolve the tag being released
        id: tag
        run: echo "tag=${{ inputs.tag || github.ref_name }}" >> "$GITHUB_OUTPUT"

      # fetch-depth: 0 so the full tag list is available to the next step.
      - uses: actions/checkout@v4
        with:
          ref: ${{ steps.tag.outputs.tag }}
          fetch-depth: 0

      # Pin the comparison base explicitly.  Left to itself, GitHub starts from
      # the previous *Release* -- and this repo has 30-odd tags but no Releases
      # yet, so the first generated notes would otherwise span the entire
      # history.  Picking the preceding vX.Y.Z tag keeps every set of notes to
      # one version's worth of changes.  Empty for the very first tag, which is
      # the one case where letting GitHub decide is correct.
      - name: Find the preceding tag
        id: prev
        run: |
          prev=$(git tag --list 'v*' --sort=-v:refname \
            | awk -v t="${{ steps.tag.outputs.tag }}" 'found { print; exit } $0 == t { found = 1 }')
          echo "Previous tag: ${prev:-<none>}"
          echo "tag=$prev" >> "$GITHUB_OUTPUT"

      - name: Create or update the GitHub Release
        uses: softprops/action-gh-release@v2
        with:
          tag_name: ${{ steps.tag.outputs.tag }}
          name: ${{ steps.tag.outputs.tag }}
          previous_tag: ${{ steps.prev.outputs.tag }}
          generate_release_notes: true