Use caching step

.github/workflows/build-charm.yaml

@@ -22,20 +22,35 @@ jobs:
     steps:
       - uses: actions/[email protected]
       - uses: canonical/[email protected]
+
+      - name: Get hash of the source
+        run: echo "SRC_HASH=${{ hashFiles('**/charms/**/*.yaml', '**/charms/**/*.py, **/charms/**/requirements.txt') }}" >> $GITHUB_ENV
+
       - name: Extract charm name
         working-directory: ${{ inputs.working-directory }}
         run: echo "CHARM_NAME=$([ -f charmcraft.yaml ] && yq '.name' charmcraft.yaml || echo UNKNOWN)" >> $GITHUB_ENV
+
+      - name: Cache charm output
+        id: cache-charm
+        uses: actions/cache@v4
+        with:
+          path: ${{ inputs.working-directory }}/packed/
+          key: ${{ runner.os}}-${{ env.CHARM_NAME }}-charm-${{ env.SRC_HASH }}
+
       - name: Pack charm
-        if: ${{ env.CHARM_NAME != 'UNKNOWN' && !cancelled() }}
+        if: ${{ env.CHARM_NAME != 'UNKNOWN' && !cancelled() && steps.cache-charm.outputs.cache-hit != 'true' }}
         working-directory: ${{ inputs.working-directory }}/${{ matrix.path }}
         run: |
           sudo snap install charmcraft --classic --channel latest/stable
           charmcraft pack -v
-          echo "CHARM_FILE=$(ls ${{env.CHARM_NAME}}_*.charm)" >> $GITHUB_ENV
+          mkdir -p packed
+          mv *.charm packed/
+          echo "CHARM_FILE=$(ls packed/${{env.CHARM_NAME}}_*.charm)" >> $GITHUB_ENV
+
       - name: Upload charm artifact
         if: ${{ env.CHARM_FILE != '' && !cancelled() }}
         uses: actions/upload-artifact@v4
         with:
           name: ${{ env.CHARM_NAME }}-charm
-          path: ${{ inputs.working-directory }}/${{ env.CHARM_FILE }}
+          path: ${{ inputs.working-directory }}/packed/${{ env.CHARM_FILE }}
           if-no-files-found: error