[mutter/wip/carlosg/clipboard-manager] ci: Check commit range more accurately

[Carlos Garnacho <carlosg src gnome org>]

commit e6244a35a08ac285025baec2f952d917ad2dc541
Author: Carlos Garnacho <carlosg gnome org>
Date:   Wed Apr 24 11:02:06 2019 +0200

    ci: Check commit range more accurately
    
    Use the requested merge branch instead of FETCH_HEAD as the other argument
    to merge-base.
    
    https://gitlab.gnome.org/GNOME/mutter/merge_requests/320

 .gitlab-ci/check-commit-log.sh | 4 ++--
 1 file changed, 2 insertions(+), 2 deletions(-)
---
diff --git a/.gitlab-ci/check-commit-log.sh b/.gitlab-ci/check-commit-log.sh
index ae696eb8b..a9056e80a 100755
--- a/.gitlab-ci/check-commit-log.sh
+++ b/.gitlab-ci/check-commit-log.sh
@@ -7,12 +7,12 @@ fi
 
 git fetch $CI_MERGE_REQUEST_PROJECT_URL.git $CI_MERGE_REQUEST_TARGET_BRANCH_NAME
 
-branch_point=$(git merge-base HEAD FETCH_HEAD)
+branch_point=$(git merge-base HEAD $CI_MERGE_REQUEST_TARGET_BRANCH_NAME)
 
 commits=$(git log --format='format:%H' $branch_point..$CI_COMMIT_SHA)
 
 if [ -z "$commits" ]; then
-  echo Commit range empty
+  echo "Commit range empty ($branch_point..$CI_COMMIT_SHA)"
   exit 1
 fi