Add OIDC-based release workflow on tag push (#22)

* Add OIDC-based release workflow on tag push

* Bump actions/checkout to v6 and drop bundler/gem_tasks

Releases now run from CI via OIDC, so the local rake release/build/install
tasks are no longer needed. Build locally with 'gem build sparoid.gemspec'
if needed.

* Update README release instructions for tag-push CI flow

* Address PR review comments

- Indent steps in main.yml under 'steps:' (cosmetic)
- Restore bundler/gem_tasks for 'rake install'; release path is now CI-only
  via the new tag-push workflow
- README: keep 'rake install' as the local install command

Author: oskgu360

.github/workflows/main.yml

@@ -14,9 +14,9 @@ jobs:
         ruby: [ 3.2, 3.3, 3.4, 4.0, ruby-head ]
     runs-on: ubuntu-latest
     steps:
-    - uses: actions/checkout@v4
-    - uses: ruby/setup-ruby@v1
-      with:
-        ruby-version: ${{ matrix.ruby }}
-        bundler-cache: true
-    - run: bundle exec rake
+      - uses: actions/checkout@v6
+      - uses: ruby/setup-ruby@v1
+        with:
+          ruby-version: ${{ matrix.ruby }}
+          bundler-cache: true
+      - run: bundle exec rake

.github/workflows/release.yml

@@ -0,0 +1,20 @@
+name: Release
+
+on:
+  push:
+    tags:
+      - 'v*'
+
+jobs:
+  release:
+    runs-on: ubuntu-latest
+    permissions:
+      contents: write
+      id-token: write
+    steps:
+      - uses: actions/checkout@v6
+      - uses: ruby/setup-ruby@v1
+        with:
+          ruby-version: '3.4'
+          bundler-cache: true
+      - uses: rubygems/release-gem@v1

README.md

@@ -34,7 +34,15 @@ Host *.example.com
 
 After checking out the repo, run `bin/setup` to install dependencies. Then, run `rake test` to run the tests. You can also run `bin/console` for an interactive prompt that will allow you to experiment.
 
-To install this gem onto your local machine, run `bundle exec rake install`. To release a new version, update the version number in `version.rb`, and then run `bundle exec rake release`, which will create a git tag for the version, push git commits and the created tag, and push the `.gem` file to [rubygems.org](https://rubygems.org).
+To install this gem onto your local machine, run `bundle exec rake install`.
+
+To release a new version:
+
+1. Bump `Sparoid::VERSION` in `lib/sparoid/version.rb` and add an entry to `CHANGELOG.md`.
+2. Open a PR with the bump, get it merged into `main`.
+3. Push a tag matching the new version, e.g. `git tag v2.1.2 && git push origin v2.1.2`.
+
+The `Release` GitHub Actions workflow then builds the gem and publishes it to [rubygems.org](https://rubygems.org) via OIDC trusted publishing — no API key required.
 
 ## Contributing