GH-331 - Set up automatic release to Maven Central.

Added a new workflow reacting to commits to the release/release branch. It consumes the release key secret for GPG signing and issues the release deployment. Polish general build to rather use environment variables for secrets rather than command line arguments.

Author: odrotbohm

.github/workflows/build.yml

@@ -24,4 +24,7 @@ jobs:
         cache: 'maven'
 
     - name: Build and deploy snapshot
-      run: ./mvnw -B deploy --file pom.xml -s settings.xml -DcentralOssrhUsername=${{ secrets.CENTRAL_OSSRH_USERNAME }} -DcentralOssrhPassword=${{ secrets.CENTRAL_OSSRH_PASSWORD }}
+      env:
+        CENTRAL_USER: ${{ secrets.CENTRAL_OSSRH_USERNAME }}
+        CENTAL_PASSWORD: ${{ secrets.CENTRAL_OSSRH_PASSWORD }}
+      run: ./mvnw -B deploy -s settings.xml

.github/workflows/release.yaml

@@ -0,0 +1,35 @@
+name: Release to Maven Central
+
+on:
+  push:
+    branches: [ release/release ]
+
+jobs:
+  build:
+    name: Release project
+    runs-on: ubuntu-latest
+
+    steps:
+
+    - name: Check out sources
+      uses: actions/checkout@v4
+
+    - name: Set up JDK 17
+      uses: actions/setup-java@v3
+      with:
+        distribution: 'temurin'
+        java-version: 17
+        cache: 'maven'
+
+    - name: Install GPG key
+      run: |
+        echo "${{ secrets.GPG_PRIVATE_KEY }}" > gpg.asc
+        echo "${{ secrets.GPG_PASSPHRASE }}" | gpg --batch --yes --passphrase-fd 0 --import gpg.asc
+
+    - name: Release to Maven Central OSSRH
+      env:
+          CENTRAL_OSSRH_USERNAME: ${{ secrets.CENTRAL_OSSRH_USERNAME }}
+          CENTRAL_OSSRH_PASSWORD: ${{ secrets.CENTRAL_OSSRH_PASSWORD }}
+          MAVEN_GPG_PASSPHRASE: ${{ secrets.GPG_PASSPHRASE }}
+      run: |
+        ./mvnw -B clean deploy -Psonatype -s settings.xml

settings.xml

@@ -4,8 +4,8 @@
 	<servers>
 		<server>
 			<id>central-ossrh</id>
-			<username>${centralOssrhUsername}</username>
-			<password>${centralOssrhPassword}</password>
+			<username>${env.CENTRAL_OSSRH_USERNAME}</username>
+			<password>${env.CENTRAL_OSSRH_PASSWORD}</password>
 		</server>
 	</servers>
 </settings>