generate docs only if squid has new commits since last run

Author: kinkie

.github/workflows/gen-docs.yaml

@@ -33,19 +33,43 @@ jobs:
         with:
           repository: squid-cache/squid
           path: squid
+      
+      - name: cache last commit hash
+        uses: actions/cache@v4
+        with:
+          path: last-squid-commit.txt
+          key: squid-last-commit-hash
+      
+      - name: Check for squid source updates
+        id: check_squid_updates
+        run: |
+          LAST_COMMIT_HASH=$(cat last-squid-commit.txt || echo "")
+          cd squid
+          CURRENT_COMMIT_HASH=$(git rev-parse HEAD)
+          echo "current=$CURRENT_COMMIT_HASH" >> $GITHUB_OUTPUT
+          if [ "$LAST_COMMIT_HASH" = "$CURRENT_COMMIT_HASH" ]; then
+            echo "marking as no no updates"
+            echo "had_update=false" >> $GITHUB_OUTPUT
+          else
+            echo "had_update=true" >> $GITHUB_OUTPUT
+          fi
+          echo $CURRENT_COMMIT_HASH > ../last-squid-commit.txt
 
       - name: Prepare squid sources
         working-directory: squid
+        if: steps.check_squid_updates.outputs.had_update == 'true'
         run: |
           ./bootstrap.sh
           . ./test-suite/buildtests/layer-02-maximus.opts
           eval ./configure $DISTCHECK_CONFIGURE_FLAGS
 
       - name: Build programming guide
+        if: steps.check_squid_updates.outputs.had_update == 'true'
         run: |
           doxygen doxyfile
 
       - name: update self
+        if: steps.check_squid_updates.outputs.had_update == 'true'
         uses: EndBug/add-and-commit@v9
         with:
           message: "automated update"