[gnome-shell] ci: Fix checking out mutter on stable branches

[Florian Müllner <fmuellner src gnome org>]

commit fd5989e99a3bbaa978c0dd4cd55d1fc677c175da
Author: Florian Müllner <fmuellner gnome org>
Date:   Wed Nov 6 20:54:57 2019 +0100

    ci: Fix checking out mutter on stable branches
    
    For stable branches, we currently only check out the correct mutter
    branch for merge requests. For the regular pipeline, our code to
    determine the current shell branch fails because CI runs on a
    temporary "pipeline/12345" branch that doesn't exist for mutter.
    
    Switching to the correct gitlab environment variable fixes that.
    
    https://gitlab.gnome.org/GNOME/gnome-shell/merge_requests/811

 .gitlab-ci/checkout-mutter.sh | 4 +---
 1 file changed, 1 insertion(+), 3 deletions(-)
---
diff --git a/.gitlab-ci/checkout-mutter.sh b/.gitlab-ci/checkout-mutter.sh
index 0193467483..9a32b6bbf3 100755
--- a/.gitlab-ci/checkout-mutter.sh
+++ b/.gitlab-ci/checkout-mutter.sh
@@ -1,6 +1,5 @@
 #!/usr/bin/bash
 
-shell_branch=$(git describe --contains --all HEAD)
 mutter_target=
 
 git clone https://gitlab.gnome.org/GNOME/mutter.git
@@ -26,8 +25,7 @@ if [ "$CI_MERGE_REQUEST_TARGET_BRANCH_NAME" ]; then
 fi
 
 if [ -z "$mutter_target" ]; then
-  mutter_target=$(git branch -r -l origin/$shell_branch)
-  mutter_target=${mutter_target:-$(git branch -r -l ${shell_branch#remotes/})}
+  mutter_target=$(git branch -r -l origin/$CI_COMMIT_REF_NAME)
   mutter_target=${mutter_target:-origin/master}
   echo Using $mutter_target instead
 fi