set SOURCE_DATE_EPOCH for reproducible builds

.github/workflows/publish-image.yml

@@ -165,11 +165,13 @@ jobs:
       # It uses the `context` parameter to define the build's context as the set of files located in the specified path. For more information, see "[Usage](https://github.com/docker/build-push-action#usage)" in the README of the `docker/build-push-action` repository.
       # It uses the `tags` and `labels` parameters to tag and label the image with the output from the "meta" step.
       # It will not push images generated from a pull request
-      - name: Set short git commit SHA
+      - name: Get short git commit SHA
         id: sha
         run: |
           calculatedSha=$(git rev-parse --short ${{ github.sha }})
           echo "COMMIT_SHORT_SHA=$calculatedSha" >> $GITHUB_ENV
+      - name: Get Git commit timestamps
+        run: echo "TIMESTAMP=$(git log -1 --pretty=%ct)" >> $GITHUB_ENV
       - name: Build and push Docker image by digest
         id: build
         uses: docker/build-push-action@v6
@@ -186,6 +188,8 @@ jobs:
           cache-to: type=gha,mode=max
           sbom: true
           outputs: type=image,"name=${{ needs.define-variables.outputs.images_list }}",push-by-digest=true,name-canonical=true,push=true
+        env:
+          SOURCE_DATE_EPOCH: ${{ env.TIMESTAMP }}
 
       # This step generates an artifact attestation for the image, which is an unforgeable statement about where and how it was built. It increases supply chain security for people who consume the image. For more information, see "[Using artifact attestations to establish provenance for builds](https://docs.github.com/en/actions/security-for-github-actions/using-artifact-attestations/using-artifact-attestations-to-establish-provenance-for-builds)." 
       - name: Generate artifact attestation (${{ needs.define-variables.outputs.ghcr_image}})