[retro-gtk/header-ci] ci: Check that private headers remain private

[Adrien Plazas <aplazas src gnome org>]

commit e902cfbe60de3bfd4fd58a7fbd0384b691b5c03e
Author: Adrien Plazas <kekun plazas laposte net>
Date:   Sat Jan 11 15:41:32 2020 +0100

    ci: Check that private headers remain private
    
    This will check we don't accidentally add private headers to public
    ones, exposing their API publicly.

 .gitlab-ci.yml | 6 ++++++
 1 file changed, 6 insertions(+)
---
diff --git a/.gitlab-ci.yml b/.gitlab-ci.yml
index 4462fbc..b613ae5 100644
--- a/.gitlab-ci.yml
+++ b/.gitlab-ci.yml
@@ -1,8 +1,14 @@
 stages:
+  - lint
   - build
   - test
   - review
 
+api-visibility:
+  stage: lint
+  script:
+    - if grep "include.*private.h" $(ls retro-gtk/*.h | grep -v private); then return 1; fi
+
 variables:
   BUNDLE: "retro-demo-samples-test-git.flatpak"