Merge branch 'disable-post-merge-ci' into 'main'

ci: Don’t run pipeline after merging a MR

See merge request GNOME/glib!3432

.gitlab-ci.yml

@@ -19,11 +19,18 @@ variables:
   G_MESSAGES_DEBUG: all
   MESON_COMMON_OPTIONS: "--buildtype debug --wrap-mode=nodownload --fatal-meson-warnings"
 
+# Default CI job setup; contrast with `.only-origin`.
+#
+# Don’t execute the pipeline when a merge request is merged into `main`, as it
+# will have already been tested
 .only-default:
   only:
     - branches
   except:
-    - tags
+    refs:
+      - tags
+    variables:
+      - $CI_PIPELINE_SOURCE == "push" && $CI_COMMIT_BRANCH == $CI_DEFAULT_BRANCH
 
 # Some jobs run on CI runners which don’t have good isolation between CI jobs,
 # and don’t have much available resource. Limit those jobs to only ones on the