Add GitHub Actions workflow to verify NIC files match source

.github/workflows/nic-integrity.yml

@@ -0,0 +1,28 @@
+name: NIC Integrity
+
+on:
+  push:
+
+jobs:
+  check:
+    runs-on: ubuntu-latest
+    env:
+      THEOS: ${{ github.workspace }}/theos
+    steps:
+      - name: Checkout repo
+        uses: actions/checkout@v4
+        with:
+          submodules: recursive
+          path: templates
+
+      - name: Checkout theos/theos
+        uses: actions/checkout@v4
+        with:
+          repository: theos/theos
+          submodules: recursive
+          path: ${{ env.THEOS }}
+
+      - name: Check
+        run: |
+          cd templates
+          ./integrity_check.sh

integrity_check.sh

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+#!/bin/bash
+
+set -e
+
+WORKSPACE_DIR=$(mktemp -d --tmpdir='' "templates.XXXXXXXXXX")
+TEMPLATES_DIR=$(pwd)
+
+# For each directory containing a valid NIC templates' source
+TEMPLATES_SOURCES=$(find "${TEMPLATES_DIR}" -type d -name NIC -exec dirname {} \;)
+
+cd "${WORKSPACE_DIR}"
+
+EXIT_CODE=0
+
+for TEMPLATES_SOURCE in $TEMPLATES_SOURCES; do
+    "${THEOS}/bin/nicify.pl" "${TEMPLATES_SOURCE}" 2> /dev/null
+    RESULT_FILE=$(ls *.nic.tar)
+    EXTRACT_DIR=$(mktemp -d -p . "${RESULT_FILE}.XXXXXXXXXX")
+    tar -xf "${TEMPLATES_DIR}/${RESULT_FILE}" -C "${EXTRACT_DIR}"
+    # thanks to https://stackoverflow.com/a/49633090
+    if ! diff -r --no-dereference --brief -x '.keep' "${TEMPLATES_SOURCE}" "${EXTRACT_DIR}"; then
+        EXIT_CODE=1
+        # per https://docs.github.com/en/actions/learn-github-actions/variables#default-environment-variables
+        if [[ "${GITHUB_ACTIONS}" = "true" ]]; then
+            # per https://docs.github.com/en/actions/using-workflows/workflow-commands-for-github-actions#setting-an-error-message
+            echo "::error file=${RESULT_FILE},title=Mismatch::The NIC file does not match the template directory"
+        fi
+    fi
+    rm -r "${EXTRACT_DIR}"
+    rm "${RESULT_FILE}"
+done
+
+rm -r "${WORKSPACE_DIR}"
+
+exit "${EXIT_CODE}"