[bbb-greenlight] Use correct variable for commit hash

[Bartłomiej Piotrowski <bpiotrowski src gnome org>]

commit a334d762cd2c3f2354efc80b276a4703a199c64f
Author: Bartłomiej Piotrowski <b bpiotrowski pl>
Date:   Mon Aug 3 13:45:57 2020 +0200

    Use correct variable for commit hash

 .gitlab-ci.yml | 4 ++--
 1 file changed, 2 insertions(+), 2 deletions(-)
---
diff --git a/.gitlab-ci.yml b/.gitlab-ci.yml
index 27a6919..e38140f 100644
--- a/.gitlab-ci.yml
+++ b/.gitlab-ci.yml
@@ -16,5 +16,5 @@ docker:
 
     - buildah login -u $CI_REGISTRY_USER -p $CI_REGISTRY_TOKEN registry.gitlab.gnome.org
     - buildah bud -t greenlight .
-    - buildah tag greenlight registry.gitlab.gnome.org/infrastructure/bbb-greenlight:$COMMIT 
registry.gitlab.gnome.org/infrastructure/bbb-greenlight:latest
-    - buildah push registry.gitlab.gnome.org/infrastructure/bbb-greenlight:$COMMIT 
registry.gitlab.gnome.org/infrastructure/bbb-greenlight:latest
+    - buildah tag greenlight registry.gitlab.gnome.org/infrastructure/bbb-greenlight:$CI_COMMIT_SHORT_SHA 
registry.gitlab.gnome.org/infrastructure/bbb-greenlight:latest
+    - buildah push registry.gitlab.gnome.org/infrastructure/bbb-greenlight:$CI_COMMIT_SHORT_SHA 
registry.gitlab.gnome.org/infrastructure/bbb-greenlight:latest