change flow of CI

.gitlab-ci.yml

 image: $CI_REGISTRY/r3/docker/julia-custom
 
 stages:
-  - test-v1.5
-  - test-v1.6
   - format-check
+  - test-required
+  - test-containers
+  - test-additional
   - deploy-doc
 
 variables:
@@ -24,18 +25,38 @@ variables:
   script:
     - Invoke-Expression $Env:ARTENOLIS_SOFT_PATH"\julia\"$Env:JULIA_VER"\bin\julia --color=yes --project=@. -e 'import Pkg; Pkg.test(; coverage = true)'"
 
+# Check the format of the code
+# --------------------------------------
+
+format:
+  stage: format-check
+  rules:
+    - if: $CI_PIPELINE_SOURCE == "external_pull_request_event"
+    - if: $CI_COMMIT_BRANCH == "master"
+  script:
+    - julia --project=@. -e 'using JuliaFormatter; format(".", verbose=true)'
+  after_script:
+    - julia --project=@. -e 'out = Cmd(`git diff --name-only`) |> read |> String;
+          if out == ""
+              exit(0)
+          else
+              @error "Some files have not been formatted!"
+              write(stdout, out)
+              exit(1)
+          end'
+
 # Test Julia v1.5
 # --------------------------------------
 
 linux:v1.5:
-  stage: test-v1.5
+  stage: test-required
   variables:
     JULIA_VER: "v1.5.3"
   <<: *global_settings
   <<: *global_testing_linux
 
 windows10:v1.5:
-  stage: test-v1.5
+  stage: test-additional
   tags:
     - windows10
   variables:
@@ -44,7 +65,7 @@ windows10:v1.5:
   <<: *global_testing_win
 
 windows8:v1.5:
-  stage: test-v1.5
+  stage: test-additional
   tags:
     - windows8
   variables:
@@ -56,7 +77,7 @@ windows8:v1.5:
 # --------------------------------------
 
 linux:v1.6:
-  stage: test-v1.6
+  stage: test-required
   needs: ["linux:v1.5"]
   variables:
     JULIA_VER: "v1.6.0"
@@ -64,7 +85,7 @@ linux:v1.6:
   <<: *global_testing_linux
 
 windows10:v1.6:
-  stage: test-v1.6
+  stage: test-additional
   needs: ["windows10:v1.5"]
   tags:
     - windows10
@@ -74,7 +95,7 @@ windows10:v1.6:
   <<: *global_testing_win
 
 windows8:v1.6:
-  stage: test-v1.6
+  stage: test-additional
   needs: ["windows8:v1.5"]
   tags:
     - windows8
@@ -87,7 +108,7 @@ windows8:v1.6:
 # --------------------------------------
 
 docker:v1.6:
-  stage: test-v1.6
+  stage: test-containers
   rules:
     - if: $CI_PIPELINE_SOURCE == "external_pull_request_event"
     - if: $CI_COMMIT_BRANCH == "master"
@@ -96,25 +117,6 @@ docker:v1.6:
   after_script:
     - julia --project=test/coverage test/coverage/coverage-summary.jl
 
-# Check the format of the code
-# --------------------------------------
-
-format:
-  stage: format-check
-  rules:
-    - if: $CI_PIPELINE_SOURCE == "external_pull_request_event"
-    - if: $CI_COMMIT_BRANCH == "master"
-  script:
-    - julia --project=@. -e 'using JuliaFormatter; format(".", verbose=true)'
-  after_script:
-    - julia --project=@. -e 'out = Cmd(`git diff --name-only`) |> read |> String;
-          if out == ""
-              exit(0)
-          else
-              @error "Some files have not been formatted!"
-              write(stdout, out)
-              exit(1)
-          end'
 
 # Deploy the documentation
 # --------------------------------------