Make COMBINE_TAG configurable and set to main as default

.gitlab-ci.yml

 stages:
+  - base
   - build
   - test
   - tag
 
-build_image:
-  stage: build
+variables:
+  COMBINE_TAG: main
+
+build_base_image:
+  stage: base
   timeout: 3 hours
   image:
     name: gcr.io/kaniko-project/executor:debug
     entrypoint: [""]
   rules:
     - changes:
-        - Dockerfile
+        - Dockerfile_base
         - packages.txt
         - requirements.txt
         - vnc/vnc_utils.sh
@@ -19,7 +23,27 @@ build_image:
   script:
     - echo "Building image - $IMAGE_DESTINATION_TAG"
     - echo "{\"auths\":{\"$CI_REGISTRY\":{\"username\":\"$CI_REGISTRY_USER\",\"password\":\"$CI_REGISTRY_PASSWORD\"}}}" > /kaniko/.docker/config.json
-    - /kaniko/executor --context "${CI_PROJECT_DIR}" --dockerfile ${CI_PROJECT_DIR}/Dockerfile --destination ${IMAGE_DESTINATION_TAG}
+    - /kaniko/executor --context "${CI_PROJECT_DIR}" --dockerfile ${CI_PROJECT_DIR}/Dockerfile_base --destination ${IMAGE_DESTINATION_TAG} --destination ${IMAGE_DESTINATION_LATEST}
+    - echo "Image pushed successfully to ${IMAGE_DESTINATION_TAG}"
+    - echo "IMAGE_NAME=${IMAGE_DESTINATION_TAG}" > .env
+  artifacts:
+    reports:
+      dotenv: .env
+  variables:
+    IMAGE_DESTINATION_TAG: ${CI_REGISTRY_IMAGE}:base-${CI_COMMIT_SHORT_SHA}
+    IMAGE_DESTINATION_LATEST: ${CI_REGISTRY_IMAGE}:base-latest
+
+
+build_image:
+  stage: build
+  timeout: 3 hours
+  image:
+    name: gcr.io/kaniko-project/executor:debug
+    entrypoint: [""]
+  script:
+    - echo "Building image - $IMAGE_DESTINATION_TAG"
+    - echo "{\"auths\":{\"$CI_REGISTRY\":{\"username\":\"$CI_REGISTRY_USER\",\"password\":\"$CI_REGISTRY_PASSWORD\"}}}" > /kaniko/.docker/config.json
+    - /kaniko/executor --context "${CI_PROJECT_DIR}" --dockerfile ${CI_PROJECT_DIR}/Dockerfile --destination ${IMAGE_DESTINATION_TAG} --build-arg "COMBINE_TAG=${COMBINE_TAG}"
     - echo "Image pushed successfully to ${IMAGE_DESTINATION_TAG}"
     - echo "IMAGE_NAME=${IMAGE_DESTINATION_TAG}" > .env
   artifacts:
@@ -60,14 +84,20 @@ build_image:
     - ls -l /code/HiggsAnalysis/CombinedLimit/data/tutorials/counting/simple-counting-experiment.root
     - text2workspace.py /code/HiggsAnalysis/CombinedLimit/data/tutorials/shapes/simple-shapes-TH1.txt
     - ls -l /code/HiggsAnalysis/CombinedLimit/data/tutorials/shapes/simple-shapes-TH1.root
-    - text2workspace.py /code/HiggsAnalysis/CombinedLimit/test/multiDim/toy-hgg-125.txt -P HiggsAnalysis.CombinedLimit.LHCHCGModels:K3 -m 125
-    - ls -l /code/HiggsAnalysis/CombinedLimit/test/multiDim/toy-hgg-125.root
+    - text2workspace.py /code/HiggsAnalysis/CombinedLimit/data/tutorials/multiDim/toy-hgg-125.txt -P HiggsAnalysis.CombinedLimit.LHCHCGModels:K3 -m 125
+    - ls -l /code/HiggsAnalysis/CombinedLimit/data/tutorials/multiDim/toy-hgg-125.root
     - combine -M Significance tests/hzz4l_datacard.txt
+    - combine /code/HiggsAnalysis/CombinedLimit/data/tutorials/CAT23001/datacard-2-template-analysis.txt -M HybridNew --LHCmode LHC-limits --rMax 2.0 --clsAcc 0.01
+    - combine /code/HiggsAnalysis/CombinedLimit/data/tutorials/CAT23001/datacard-3-parametric-analysis.txt -M HybridNew --LHCmode LHC-significance -T 100000 --mass 125
+    - combine /code/HiggsAnalysis/CombinedLimit/data/tutorials/CAT23001/datacard-3-parametric-analysis.txt -M Significance --mass 125
+    - combine /code/HiggsAnalysis/CombinedLimit/data/tutorials/CAT23001/datacard-1-counting-experiment.txt -M MarkovChainMC --tries 100
+    - text2workspace.py /code/HiggsAnalysis/CombinedLimit/data/tutorials/CAT23001/datacard-5-multi-signal.txt -P HiggsAnalysis.CombinedLimit.PhysicsModel:floatingXSHiggs --PO modes=ggH,qqH -o datacard-5-multi-signal.root --mass 125
+    - combine /code/HiggsAnalysis/CombinedLimit/data/tutorials/CAT23001/datacard-5-multi-signal.root -M MultiDimFit --algo singles --mass 125
+    - combine /code/HiggsAnalysis/CombinedLimit/data/tutorials/CAT23001/datacard-5-multi-signal.txt -M ChannelCompatibilityCheck --mass 125
+
 
 test_image:
   <<: *test_image_template
-  rules:
-    - !reference [build_image, rules]
 
 tag_image_latest:
   stage: tag