[gnome-shell] ci: Fix identifying commits in MR

[Florian Müllner <fmuellner src gnome org>]

commit 1b7ff760924d9a8544f32da937e89d0e23de68b2
Author: Florian Müllner <fmuellner gnome org>
Date:   Thu Jul 25 22:26:19 2019 +0200

    ci: Fix identifying commits in MR
    
    When a MR uses a private namespace, "origin" refers to that, and its
    master branch may be outdated with regard to upstream master.
    
    We are really only interested in checking the line changes from the commits
    in the MR, so figure out the correct branch point instead.
    
    https://gitlab.gnome.org/GNOME/gnome-shell/merge_requests/647

 .gitlab-ci/run-eslint.sh | 5 ++++-
 1 file changed, 4 insertions(+), 1 deletion(-)
---
diff --git a/.gitlab-ci/run-eslint.sh b/.gitlab-ci/run-eslint.sh
index 4732f986f..0f745a58d 100755
--- a/.gitlab-ci/run-eslint.sh
+++ b/.gitlab-ci/run-eslint.sh
@@ -67,7 +67,10 @@ create_common() {
 }
 
 if [ "$CI_MERGE_REQUEST_TARGET_BRANCH_NAME" ]; then
-  commit_range=origin/$CI_MERGE_REQUEST_TARGET_BRANCH_NAME...$CI_COMMIT_SHA
+  git fetch $CI_MERGE_REQUEST_PROJECT_URL.git $CI_MERGE_REQUEST_TARGET_BRANCH_NAME
+  branch_point=$(git merge-base HEAD FETCH_HEAD)
+  commit_range=$branch_point...$CI_COMMIT_SHA
+
   list_commit_range_additions $commit_range > $LINE_CHANGES
 
   # Don't bother with running lint when no JS changed