ci: try to fix unittest triggering when skip tests message is included

.gitlab-ci.yml

@@ -1,7 +1,5 @@
-# a single stage allows test to run even if flake8 fails,
-# and makes it possible to get all the errors at once
 stages:
-  - pre_release
+  - pre_release # a single stage allows test to run even if flake8 fails and makes it possible to get all the errors at once
   - release
   - deploy
 
@@ -27,16 +25,22 @@ zip:
       - mixer
     expire_in: 1 week
 
+# Note: you cannot extend this job with another only: variables job
+# If you need that, you should rewrite and combine the rules
 .only_on_gitlab.com:
   only:
     variables:
       - $CI_SERVER_URL == "https://gitlab.com"
 
+# Note: you cannot extend this job with another except: variables job
+# If you need that, you should rewrite and combine the rules
 .exclude_on_gitlab.com:
   except:
     variables:
       - $CI_SERVER_URL == "https://gitlab.com"
 
+# Note: you cannot extend this job with another only: variables job
+# If you need that, you should rewrite and combine the rules
 .on_version_tag:
   only:
     refs:
@@ -64,9 +68,6 @@ release:
   stage: pre_release
   tags:
     - blender
-  except:
-    variables:
-      - $CI_COMMIT_MESSAGE =~ /\[skip-tests\]/
   variables:
     MIXER_BLENDER_ZIP_BASENAME: blender-2.83.4-windows64
     MIXER_BLENDER_VERSION_BASE: "2.83"
@@ -84,17 +85,27 @@ release:
     reports:
       junit:
         - logs\tests\*.xml
-
+  
 unittest:
   extends:
     - .base_unittest
-    - .exclude_on_gitlab.com
+  except:
+    variables:
+      - $CI_COMMIT_MESSAGE =~ /\[skip-tests\]/
+      - $CI_SERVER_URL == "https://gitlab.com"
 
 unittest_gitlab.com:
   extends:
     - .base_unittest
-    - .only_on_gitlab.com
-    - .on_version_tag
+  except:
+    variables:
+      - $CI_COMMIT_MESSAGE =~ /\[skip-tests\]/
+  only:
+    refs:
+      # see inject_version.py
+      - /^v([0-9]+)\.([0-9]+)\.([0-9]+)(\-[0-9A-Za-z-]+)?(\+[0-9A-Za-z-]+)?$/
+    variables:
+      - $CI_SERVER_URL == "https://gitlab.com"
 
 .deploy_network_folder:
   extends: