chore(ci): lint with yamllint

.github/workflows/build-rock.yaml

@@ -14,7 +14,7 @@ jobs:
     steps:
       - name: Checkout repository
         uses: actions/checkout@v4
-    
+
       - name: Build rock
         uses: canonical/craft-actions/rockcraft-pack@main
         with:

.github/workflows/run-linters.yaml

@@ -15,7 +15,8 @@ jobs:
       - name: Install dependencies
         run: |
           sudo snap install shellcheck
-      
+          pip install -U yamllint
+
       - name: Checkout repository
         uses: actions/checkout@v4
         with:
@@ -25,3 +26,7 @@ jobs:
       - name: Run ShellCheck
         run: |
           ./tools/external/snapd-testing-tools/utils/spread-shellcheck tests/spread/ spread.yaml
+
+      - name: Run yamllint
+        run: |
+          yamllint --strict .

.yamllint.yaml

@@ -0,0 +1,11 @@
+---
+
+extends: relaxed
+
+ignore:
+  - 'tools/external/'
+
+rules:
+  # Disable line length limit because the build scripts can
+  # get fairly long
+  line-length: disable

rockcraft.yaml

@@ -117,4 +117,3 @@ services:
       SNAPCRAFT_BUILD_ENVIRONMENT: host
       # put libexec on the path, for craftctl
       PATH: /usr/libexec/snapcraft:/usr/local/sbin:/usr/local/bin:/usr/sbin:/usr/bin:/sbin:/bin
-

spread.yaml

@@ -12,8 +12,8 @@ environment:
   SNAPCRAFT_BUILD_BASE: core22
 
 include:
-    - tests/
-    - tools/
+  - tests/
+  - tools/
 
 backends:
   google:
@@ -69,11 +69,11 @@ prepare: |
     snap install docker --channel=core18/stable
   else
     snap install docker
-  fi  
+  fi
 
   # make sure docker is working
   retry -n 10 --wait 2 sh -c 'docker run --rm hello-world'
-  
+
   # install rockcraft just to use its bundled skopeo
   snap install --classic --stable rockcraft