chore: add commitlint

Also add separate contributing guideline file.

Author: BlasiusSecundus

.github/workflows/pull-request.yml

@@ -10,14 +10,29 @@ jobs:
     steps:
       - uses: actions/checkout@v2
       - uses: gradle/wrapper-validation-action@v1
+  commitlint:
+    name: Validate conventional commits
+    runs-on: ubuntu-latest
+    needs: validation
+    steps:
+      - uses: actions/checkout@v2
+        name: Checkout
+        with:
+          fetch-depth: 0
+      - uses: actions/setup-node@v1
+        name: Setup Node
+        with:
+          node-version: 14
+      - run: cd commitlint && npm ci && npm audit && git ls-remote https://github.com/graphql-java-kickstart/graphql-spring-boot.git HEAD | grep -o '[0-9a-f]*' | xargs -I{} npx commitlint --from {} --verbose
+        name: Run commitlint
   test:
     name: Test run
     strategy:
       fail-fast: false
       matrix:
         os: [ ubuntu-latest, macos-latest, windows-latest ]
         java: [ 8, 11, 15 ]
-    needs: validation
+    needs: [validation, commitlint]
     runs-on: ${{ matrix.os }}
     steps:
       - name: Checkout
@@ -50,7 +65,7 @@ jobs:
         run: gradlew --info check
   build:
     name: Sonar analysis
-    needs: validation
+    needs: [validation, commitlint]
     runs-on: ubuntu-latest
     env:
       SONAR_TOKEN: ${{ secrets.SONAR_TOKEN }}

.gitignore

@@ -63,3 +63,8 @@ fabric.properties
 # Mac
 
 .DS_Store
+
+# Node
+
+**/node_modules
+**/.husky

CONTRIBUTING.md

@@ -0,0 +1,23 @@
+
+###Commit messages
+
+This project uses the [Conventional Commits](https://www.conventionalcommits.org) specification for commit messages.
+The CI pipeline validates that commit messages adhere to the specification using 
+[commitlint](https://github.com/conventional-changelog/commitlint).
+
+**Note**: *Historical commits, made before applying this convention may not fulfill the requirements of the 
+specification. These commits are exempt from this check.*
+
+To check commit messages before committing, go to the `commitlint` folder and run `npm ci && npm run add-commitlint-git-hook` 
+(you will need NodeJS installed on your machine). This command sets up a git hook to run commitlint before each commit,
+to prevent committing with invalid commit messages in the first place.
+
+**Note**: *Please always use `npm ci` instead of `install` to prevent unwanted changes to `package-lock.json`.*
+
+To remove the git hook, just delete the `commitlint/.husky` folder.
+
+As for the optional scope part of the commit message:
+- if your commit addresses an issue, please refer the issue number in the scope - e.g. `fix(#123): ...`
+- otherwise, if applicable, please use the modified / affected subproject name, without the repetitive prefix/postfix 
+  parts (like `graphql-kickstart-spring-boot`, `spring-boot-starter` or `autoconfigure`) - e.g. `feat(webflux): ...`  
+

commitlint/commitlint.config.js

@@ -0,0 +1 @@
+module.exports = {extends: ['@commitlint/config-conventional']}