ci: Check that pot file is generated correctly

This is to guard against the now infamous xgettext bug[0].

[0] https://savannah.gnu.org/bugs/?50920#comment5

https://gitlab.gnome.org/GNOME/gnome-shell/merge_requests/408

.gitlab-ci.yml

@@ -6,6 +6,7 @@ stages:
 
 variables:
     JS_LOG: "js-report.txt"
+    POT_LOG: "pot-update.txt"
 
 .only_default: &only_default
     only:
@@ -71,3 +72,19 @@ test:
         paths:
             - build/meson-logs/testlog.txt
         when: on_failure
+
+test-pot:
+    image: registry.gitlab.gnome.org/gnome/gnome-shell/master:v1
+    stage: test
+    before_script:
+        - ninja -C mutter/build install
+    script:
+        # Check that pot files are generated correctly:
+        # https://savannah.gnu.org/bugs/?50920#comment5
+        - ninja -C build gnome-shell-pot 2>&1 | awk '
+            BEGIN { start=0; }
+            start==1 { print $0; }
+            /gnome-shell-pot/ { start=1; }
+          ' | tee $POT_LOG
+        - (! grep -q . $POT_LOG)
+    <<: *only_default