[CI/Build] Add linting for excalidraw exported images

Ensure that PNG images named as excalidraw images were exported with
the excalidraw metadata embedded in them. This ensures they are
editable in the future.

Signed-off-by: Russell Bryant <rbryant@redhat.com>

.github/workflows/png-lint.yml

@@ -0,0 +1,37 @@
+name: Lint PNG exports from excalidraw
+on:
+  push:
+    branches:
+      - "main"
+    paths:
+      - '*.excalidraw.png'
+      - '.github/workflows/png-lint.yml'
+  pull_request:
+    branches:
+      - "main"
+    paths:
+      - '*.excalidraw.png'
+      - '.github/workflows/png-lint.yml'
+
+env:
+  LC_ALL: en_US.UTF-8
+
+defaults:
+  run:
+    shell: bash
+
+permissions:
+  contents: read
+
+jobs:
+  actionlint:
+    runs-on: ubuntu-latest
+    steps:
+      - name: "Checkout"
+        uses: actions/checkout@11bd71901bbe5b1630ceea73d27597364c9af683 # v4.2.2
+        with:
+          fetch-depth: 0
+
+      - name: "Run png-lint.sh to check excalidraw exported images"
+        run: |
+          tools/png-lint.sh

format.sh

@@ -299,6 +299,10 @@ echo 'vLLM shellcheck:'
 tools/shellcheck.sh
 echo 'vLLM shellcheck: Done'
 
+echo 'excalidraw png check:'
+tools/png-lint.sh
+echo 'excalidraw png check: Done'
+
 if ! git diff --quiet &>/dev/null; then
     echo 
     echo "🔍🔍There are files changed by the format checker or by you that are not added and committed:"

tools/png-lint.sh

@@ -0,0 +1,15 @@
+#!/bin/bash
+
+# Ensure that *.excalidraw.png files have the excalidraw metadata
+# embedded in them. This ensures they can be loaded back into
+# the tool and edited in the future.
+
+for file in $(find . -iname '*.excalidraw.png'); do
+	if git check-ignore -q "$file"; then
+		continue
+	fi
+	if ! grep -q "excalidraw+json" "$file"; then
+		echo "$file was not exported from excalidraw with 'Embed Scene' enabled."
+		exit 1
+	fi
+done