chore(CI): build image on tag & tag images with short sha instead of date

.gitlab-ci.yml

@@ -1,15 +1,13 @@
 include:
   - component: $CI_SERVER_FQDN/$CI_PROJECT_PATH/nix-gitlab-ci@$CI_COMMIT_SHA
-
 stages:
   - build
   - trigger
-
 build:image:
   stage: build
   parallel:
     matrix:
-      - VARIANT: [ "", "-cachix", "-attic" ]
+      - VARIANT: ["", "-cachix", "-attic"]
   image: nixpkgs/nix-flakes:latest
   before_script:
     - nix profile install nixpkgs#skopeo
@@ -17,9 +15,18 @@ build:image:
   script:
     - nix build .#image${VARIANT}
     - export NORMALIZED_BRANCH=${CI_COMMIT_BRANCH/\//-}
-    - skopeo --insecure-policy copy  --dest-creds "${CI_REGISTRY_USER}:${CI_REGISTRY_PASSWORD}" --tmpdir /tmp
-      "docker-archive:result"
-      "docker://$CI_REGISTRY_IMAGE/nix-ci:${NORMALIZED_BRANCH/main/latest}${VARIANT}"
-    - skopeo --insecure-policy copy --dest-creds "${CI_REGISTRY_USER}:${CI_REGISTRY_PASSWORD}" --tmpdir /tmp
-      "docker-archive:result"
-      "docker://$CI_REGISTRY_IMAGE/nix-ci:$(date +"%m-%d-%y")${VARIANT}"
+    - skopeo --insecure-policy copy --dest-creds "${CI_REGISTRY_USER}:${CI_REGISTRY_PASSWORD}" --tmpdir /tmp "docker-archive:result" "docker://$CI_REGISTRY_IMAGE/nix-ci:${CI_COMMIT_SHORT_SHA}${VARIANT}"
+    # branches
+    - |
+      if [ -z "$CI_COMMIT_TAG" ]; then
+        skopeo --insecure-policy copy --dest-creds "${CI_REGISTRY_USER}:${CI_REGISTRY_PASSWORD}" --tmpdir /tmp \
+          "docker-archive:result" \
+          "docker://$CI_REGISTRY_IMAGE/nix-ci:${NORMALIZED_BRANCH/main/latest}${VARIANT}";
+      fi
+    # tags
+    - |
+      if [ -n "$CI_COMMIT_TAG" ]; then
+        skopeo --insecure-policy copy --dest-creds "${CI_REGISTRY_USER}:${CI_REGISTRY_PASSWORD}" --tmpdir /tmp \
+          "docker-archive:result" \
+          "docker://$CI_REGISTRY_IMAGE/nix-ci:${CI_COMMIT_TAG}${VARIANT}";
+      fi