[gnome-flashback] ci: validate menu file

[Alberts Muktupāvels <muktupavels src gnome org>]

commit e2ed1e0020e98407c3690db40b3902dd584c4f94
Author: Alberts Muktupāvels <alberts muktupavels gmail com>
Date:   Fri Mar 20 21:45:26 2020 +0200

    ci: validate menu file

 .gitlab-ci.yml | 14 ++++++++++++++
 1 file changed, 14 insertions(+)
---
diff --git a/.gitlab-ci.yml b/.gitlab-ci.yml
index f98c875..a2f376e 100644
--- a/.gitlab-ci.yml
+++ b/.gitlab-ci.yml
@@ -1,10 +1,24 @@
 stages:
+  - validate
   - build
   - analysis
 
 variables:
   GIT_SUBMODULE_STRATEGY: normal
 
+validate-menu:
+  image: ubuntu:devel
+  stage: validate
+  except:
+    - tags
+  before_script:
+    - apt-get update
+    - apt-get install -q -y --no-install-recommends libxml2-utils
+  script:
+    - xmllint --noblanks --noout
+      --path https://standards.freedesktop.org/menu-spec/menu-latest.dtd
+      data/menus/gnome-flashback-applications.menu
+
 build-ubuntu:
   image: ubuntu:devel
   stage: build