ci: Use shared checks

This allows to drop the custom check-po

Part-of: <https://gitlab.gnome.org/GNOME/calls/-/merge_requests/753>

.gitlab-ci/commit-rules.yml

@@ -0,0 +1,20 @@
+patterns:
+  deny:
+    - regex: '^$CI_MERGE_REQUEST_PROJECT_URL/(-/)?merge_requests/$CI_MERGE_REQUEST_IID$'
+      message: Commit message must not contain a link to its own merge request
+    - regex: '^[^:]+: [a-z]'
+      message: "Commit description in commit message subject should be properly Capitalized. E.g. 'monitor: Avoid crash on unplug'"
+      where: subject
+    - regex: '^\S*\.(c|h|ui):'
+      message: Commit message subject prefix should not include .c, .h etc.
+      where: subject
+    - regex: '([^.]\.|[:,;])\s*$'
+      message: Commit message subject should not end with punctuation
+      where: subject
+    - regex: '^[A-Z]\S*:'
+      message: "Identifier in commit message subject should start lowercase 'monitor: Avoid crash on unplug'"
+      where: subject
+  require:
+    - regex: '^[a-z0-9,\.\+\-/#=_]+:'
+      message: "Commit message should start with a lowercase identifier 'monitor: Avoid crash on unplug'"
+      where: subject