Add actionlint workflow

.github/actionlint.yaml

@@ -0,0 +1,21 @@
+self-hosted-runner:
+  # Labels of self-hosted runner in array of strings.
+  labels: []
+
+# Configuration variables in array of strings defined in your repository or
+# organization. `null` means disabling configuration variables check.
+# Empty array means no configuration variable is allowed.
+config-variables: null
+
+# Configuration for file paths. The keys are glob patterns to match to file
+# paths relative to the repository root. The values are the configurations for
+# the file paths. Note that the path separator is always '/'.
+# The following configurations are available.
+#
+# "ignore" is an array of regular expression patterns. Matched error messages
+# are ignored. This is similar to the "-ignore" command line option.
+paths:
+  .github/workflows/ci.yml:
+    ignore:
+      - 'file "/bin/sh" does not exist in .+'
+      - 'missing input "args" which is required by action "Promtool".+'

.github/actions/promtool/action.yml

@@ -1,4 +1,5 @@
 name: Promtool
+description: This is an action to access Prometheus Tooling via the promtool command
 
 inputs:
   args:

.github/workflows/actionlint.yml

@@ -0,0 +1,12 @@
+name: Lint GitHub Actions
+on:
+  push:
+    paths: ['.github/**']
+jobs:
+  actionlint:
+    runs-on: ubuntu-latest
+    steps:
+      - uses: actions/checkout@v4
+        with:
+          show-progress: false
+      - uses: alphagov/govuk-infrastructure/.github/actions/actionlint@main

.github/workflows/ci.yml

@@ -32,7 +32,7 @@
           done
 
       - name: Read Kubernetes version from /kubernetes_version
-        run: "grep KUBERNETES_VERSION kubernetes_version >> $GITHUB_ENV"
+        run: grep KUBERNETES_VERSION kubernetes_version >> "$GITHUB_ENV"
 
       - name: kubeconform
         uses: docker://ghcr.io/yannh/kubeconform:latest-alpine
@@ -71,12 +71,12 @@
         with:
           show-progress: false
       - name: Run promtool checks
         uses: ./.github/actions/promtool
         with:
           args: >
             check rules $(find charts/monitoring-config/rules -name '*.yaml' \
               -not -name '*_tests.yaml')
       - name: Run promtool tests
         uses: ./.github/actions/promtool
         with:
           args: test rules charts/monitoring-config/rules/*_tests.yaml