feat(CI): add a GitHub Action to lint the YAML

- Run only on pull request
- Add a `.yamllint` config file
- Lint YAML

4 files changed, 118 insertions, 107 deletions

diff --git a/.github/workflows/build.yml b/.github/workflows/build.yml
index 811a11cf5..bbb6c1d29 100644
--- a/.github/workflows/build.yml
+++ b/.github/workflows/build.yml
@@ -8,11 +8,11 @@ jobs:
     env:
       MRUBY_CONFIG: travis
     steps:
-    - uses: actions/checkout@v1
-    - name: apt
-      run: sudo apt install ruby gperf
-    - name: build and test
-      run: rake -m -j4 gensym all test
+      - uses: actions/checkout@v1
+      - name: apt
+        run: sudo apt install ruby gperf
+      - name: build and test
+        run: rake -m -j4 gensym all test
 
   Ubuntu-1804-gcc:
     runs-on: ubuntu-18.04
@@ -21,11 +21,11 @@ jobs:
       CC: gcc
       CXX: g++
     steps:
-    - uses: actions/checkout@v1
-    - name: apt
-      run: sudo apt install ruby gperf gcc g++
-    - name: build and test
-      run: rake -m -j4 gensym all test
+      - uses: actions/checkout@v1
+      - name: apt
+        run: sudo apt install ruby gperf gcc g++
+      - name: build and test
+        run: rake -m -j4 gensym all test
 
   Ubuntu-1804-clang:
     runs-on: ubuntu-18.04
@@ -34,22 +34,22 @@ jobs:
       CC: clang
       CXX: clang++
     steps:
-    - uses: actions/checkout@v1
-    - name: apt
-      run: sudo apt install ruby gperf
-    - name: build and test
-      run: rake -m -j4 gensym all test
+      - uses: actions/checkout@v1
+      - name: apt
+        run: sudo apt install ruby gperf
+      - name: build and test
+        run: rake -m -j4 gensym all test
 
   macOS:
     runs-on: macos-latest
     env:
       MRUBY_CONFIG: travis
     steps:
-    - uses: actions/checkout@v1
-    - name: brew
-      run: brew install ruby gperf
-    - name: build and test
-      run: rake -m -j4 gensym all test
+      - uses: actions/checkout@v1
+      - name: brew
+        run: brew install ruby gperf
+      - name: build and test
+        run: rake -m -j4 gensym all test
 
   Windows-MinGW:
     runs-on: windows-latest
@@ -57,11 +57,11 @@ jobs:
       MRUBY_CONFIG: travis
       CFLAGS: -g -O1 -Wall -Wundef
     steps:
-    - uses: actions/checkout@v1
-    - name: chocolatey
-      run: choco install -y ruby gperf
-    - name: build
-      run: rake -E 'STDOUT.sync=true' -j4 gensym all test
+      - uses: actions/checkout@v1
+      - name: chocolatey
+        run: choco install -y ruby gperf
+      - name: build
+        run: rake -E 'STDOUT.sync=true' -j4 gensym all test
 
   Windows-Cygwin:
     runs-on: windows-latest
@@ -69,25 +69,25 @@ jobs:
       MRUBY_CONFIG: travis
       ACTIONS_ALLOW_UNSECURE_COMMANDS: true
     steps:
-    - uses: actions/checkout@v1
-    - uses: actions/cache@v1
-      with:
-        path: C:\Users\runneradmin\AppData\Local\Temp\chocolatey
-        key: ${{ runner.os }}-cygwin-chocolatey-${{ matrix.os }}-${{ github.sha }}
-        restore-keys: |
-          ${{ runner.os }}-cygwin-chocolatey-${{ matrix.os }}-
-          ${{ runner.os }}-cygwin-chocolatey-
-    - name: chocolatey
-      run: choco install -y cygwin
-    - name: Install cygwin packages
-      shell: cmd
-      run: C:\tools\cygwin\cygwinsetup.exe -qgnNdO -R C:/tools/cygwin -l C:/tools/cygwin/package -s http://mirrors.kernel.org/sourceware/cygwin/ -P gcc-core,gcc-g++,make,gperf,ruby
-    - name: Set ENV
-      run: |
-        echo '::set-env name=PATH::C:\tools\cygwin\bin;C:\tools\cygwin\usr\bin'
-    - name: build and test
-      shell: cmd
-      run: C:\tools\cygwin\bin\ruby.exe /usr/bin/rake -E 'STDOUT.sync=true' -m gensym all test
+      - uses: actions/checkout@v1
+      - uses: actions/cache@v1
+        with:
+          path: C:\Users\runneradmin\AppData\Local\Temp\chocolatey
+          key: ${{ runner.os }}-cygwin-chocolatey-${{ matrix.os }}-${{ github.sha }}
+          restore-keys: |
+            ${{ runner.os }}-cygwin-chocolatey-${{ matrix.os }}-
+            ${{ runner.os }}-cygwin-chocolatey-
+      - name: chocolatey
+        run: choco install -y cygwin
+      - name: Install cygwin packages
+        shell: cmd
+        run: C:\tools\cygwin\cygwinsetup.exe -qgnNdO -R C:/tools/cygwin -l C:/tools/cygwin/package -s http://mirrors.kernel.org/sourceware/cygwin/ -P gcc-core,gcc-g++,make,gperf,ruby
+      - name: Set ENV
+        run: |
+          echo '::set-env name=PATH::C:\tools\cygwin\bin;C:\tools\cygwin\usr\bin'
+      - name: build and test
+        shell: cmd
+        run: C:\tools\cygwin\bin\ruby.exe /usr/bin/rake -E 'STDOUT.sync=true' -m gensym all test
 
   Windows-VC:
     runs-on: windows-latest
@@ -97,11 +97,11 @@ jobs:
       CFLAGS: "/c /nologo /W3 /we4013 /Zi /MD /D_CRT_SECURE_NO_WARNINGS"
       CXXFLAGS: "/c /nologo /W3 /Zi /MD /EHs /D_CRT_SECURE_NO_WARNINGS"
     steps:
-    - uses: actions/checkout@v1
-    - name: chocolatey
-      run: choco install -y ruby gperf
-    - name: build and test
-      shell: cmd
-      run: |
-        call "C:\Program Files (x86)\Microsoft Visual Studio\2019\Enterprise\VC\Auxiliary\Build\vcvars64.bat"
-        rake -E "STDOUT.sync=true" gensym all test
+      - uses: actions/checkout@v1
+      - name: chocolatey
+        run: choco install -y ruby gperf
+      - name: build and test
+        shell: cmd
+        run: |
+          call "C:\Program Files (x86)\Microsoft Visual Studio\2019\Enterprise\VC\Auxiliary\Build\vcvars64.bat"
+          rake -E "STDOUT.sync=true" gensym all test
diff --git a/.github/workflows/codeql-analysis.yml b/.github/workflows/codeql-analysis.yml
index efbc25e93..ea9f9bd8e 100644
--- a/.github/workflows/codeql-analysis.yml
+++ b/.github/workflows/codeql-analysis.yml
@@ -12,40 +12,40 @@ jobs:
     runs-on: ubuntu-latest
 
     steps:
-    - name: Checkout repository
-      uses: actions/checkout@v2
-      with:
-        # We must fetch at least the immediate parents so that if this is
-        # a pull request then we can checkout the head.
-        fetch-depth: 2
-
-    # If this run was triggered by a pull request event, then checkout
-    # the head of the pull request instead of the merge commit.
-    - run: git checkout HEAD^2
-      if: ${{ github.event_name == 'pull_request' }}
-
-    # Initializes the CodeQL tools for scanning.
-    - name: Initialize CodeQL
-      uses: github/codeql-action/init@v1
-      # Override language selection by uncommenting this and choosing your languages
-      # with:
-      #   languages: go, javascript, csharp, python, cpp, java
-
-    # Autobuild attempts to build any compiled languages  (C/C++, C#, or Java).
-    # If this step fails, then you should remove it and run the build manually (see below)
-    - name: Autobuild
-      uses: github/codeql-action/autobuild@v1
-
-    # ℹ️ Command-line programs to run using the OS shell.
-    # 📚 https://git.io/JvXDl
-
-    # ✏️ If the Autobuild fails above, remove it and uncomment the following three lines
-    #    and modify them (or add more) to build your code if your project
-    #    uses a compiled language
-
-    #- run: |
-    #   make bootstrap
-    #   make release
-
-    - name: Perform CodeQL Analysis
-      uses: github/codeql-action/analyze@v1
+      - name: Checkout repository
+        uses: actions/checkout@v2
+        with:
+          # We must fetch at least the immediate parents so that if this is
+          # a pull request then we can checkout the head.
+          fetch-depth: 2
+
+      # If this run was triggered by a pull request event, then checkout
+      # the head of the pull request instead of the merge commit.
+      - run: git checkout HEAD^2
+        if: ${{ github.event_name == 'pull_request' }}
+
+      # Initializes the CodeQL tools for scanning.
+      - name: Initialize CodeQL
+        uses: github/codeql-action/init@v1
+        # Override language selection by uncommenting this and choosing your languages
+        # with:
+        #   languages: go, javascript, csharp, python, cpp, java
+
+      # Autobuild attempts to build any compiled languages  (C/C++, C#, or Java).
+      # If this step fails, then you should remove it and run the build manually (see below)
+      - name: Autobuild
+        uses: github/codeql-action/autobuild@v1
+
+      # ℹ️ Command-line programs to run using the OS shell.
+      # 📚 https://git.io/JvXDl
+
+      # ✏️ If the Autobuild fails above, remove it and uncomment the following three lines
+      #    and modify them (or add more) to build your code if your project
+      #    uses a compiled language
+
+      # - run: |
+      #    make bootstrap
+      #    make release
+
+      - name: Perform CodeQL Analysis
+        uses: github/codeql-action/analyze@v1
diff --git a/.github/workflows/lint.yml b/.github/workflows/lint.yml
new file mode 100644
index 000000000..e04d0fc75
--- /dev/null
+++ b/.github/workflows/lint.yml
@@ -0,0 +1,12 @@
+name: ❄️ Lint
+
+on: [pull_request]
+
+jobs:
+  yamllint:
+    name: 🍶 YAML
+    runs-on: ubuntu-latest
+    steps:
+      - uses: actions/checkout@v2
+      - name: 🧹 YAML Lint
+        uses: ibiqlik/action-yamllint@v3
diff --git a/.github/workflows/main.yml b/.github/workflows/main.yml
index 3c1a7e07e..60414e7dc 100644
--- a/.github/workflows/main.yml
+++ b/.github/workflows/main.yml
@@ -4,21 +4,20 @@ jobs:
   Fuzzing:
     runs-on: ubuntu-latest
     steps:
-    - name: Build Fuzzers
-      uses: google/oss-fuzz/infra/cifuzz/actions/build_fuzzers@master
-      with:
-        oss-fuzz-project-name: 'mruby'
-        dry-run: false
-    - name: Run Fuzzers
-      uses: google/oss-fuzz/infra/cifuzz/actions/run_fuzzers@master
-      with:
-        oss-fuzz-project-name: 'mruby'
-        fuzz-seconds: 600
-        dry-run: false
-    - name: Upload Crash
-      uses: actions/upload-artifact@v1
-      if: failure()
-      with:
-        name: artifacts
-        path: ./out/artifacts
-
+      - name: Build Fuzzers
+        uses: google/oss-fuzz/infra/cifuzz/actions/build_fuzzers@master
+        with:
+          oss-fuzz-project-name: 'mruby'
+          dry-run: false
+      - name: Run Fuzzers
+        uses: google/oss-fuzz/infra/cifuzz/actions/run_fuzzers@master
+        with:
+          oss-fuzz-project-name: 'mruby'
+          fuzz-seconds: 600
+          dry-run: false
+      - name: Upload Crash
+        uses: actions/upload-artifact@v1
+        if: failure()
+        with:
+          name: artifacts
+          path: ./out/artifacts