Update .gitlab-ci.yml

.gitlab-ci.yml

@@ -40,7 +40,7 @@ test:
 #      when: never
     - if: '$CI_COMMIT_BRANCH'
 
-# generate documentation when commiting to master
+# generate documentation when commiting to master and the VERSION.txt file has changed
 document:
   stage: document
   script:
@@ -49,6 +49,8 @@ document:
     - shared-fi
   rules:
     - if: '$CI_COMMIT_BRANCH == "master"'
+      changes:
+        - VERSION.txt
     - if: '$CI_COMMIT_BRANCH'
       when: never
   artifacts: