Add gem push workflow

.github/scripts/check-release.sh

@@ -0,0 +1,13 @@
+#!/bin/sh
+
+# Checking if current tag matches the package version.
+current_tag=$(echo $GITHUB_REF | cut -d '/' -f 3 | sed -r 's/^v//')
+file_tag=$(grep 'VERSION = ' lib/phlex/icons/version.rb | cut -d '=' -f 2- | tr -d ' ' | tr -d \')
+if [ "$current_tag" != "$file_tag" ]; then
+  echo "Error: the current tag does not match the version in package file(s)."
+  echo "$current_tag vs $file_tag"
+  exit 1
+fi
+
+echo 'OK'
+exit 0

.github/workflows/gem-push.yml

@@ -0,0 +1,33 @@
+name: Release Gem to RubyGems.org
+
+on:
+  release:
+    types: [published]
+
+jobs:
+  build-and-publish:
+    name: Build and Publish Package to RubyGems.org
+    runs-on: ubuntu-latest
+
+    steps:
+      - name: Checkout code
+        uses: actions/checkout@v4
+
+      - name: Set up Ruby 3.3.4
+        uses: ruby/setup-ruby@v1
+        with:
+          ruby-version: 3.3.4
+
+      - name: Check release validity
+        run: sh .github/scripts/check-release.sh
+
+      - name: Publish to RubyGems
+        env:
+          GEM_HOST_API_KEY: ${{secrets.RUBYGEMS_AUTH_TOKEN}}
+        run: |
+          mkdir -p $HOME/.gem
+          touch $HOME/.gem/credentials
+          chmod 0600 $HOME/.gem/credentials
+          printf -- "---\n:rubygems_api_key: ${GEM_HOST_API_KEY}\n" > $HOME/.gem/credentials
+          gem build phlex-icons.gemspec
+          gem push *.gem