[mutter] ci: Nag about invalid commit message subject prefixes

[Georges Basile Stavracas Neto <gbsneto src gnome org>]

commit 7b3dee2d9706753bc1f8bf13ada66ab51df45b06
Author: Jonas Ådahl <jadahl gmail com>
Date:   Mon Apr 1 13:10:10 2019 +0200

    ci: Nag about invalid commit message subject prefixes
    
    Prefixes use an abbreviated form of the module or section being changed.
    For example, changes to MetaBackend/meta-backend.c are prefixed with
    `backend:` and generic changes to src/x11/ are prefixed `x11:`.
    
    This extra nit picking check is meant to avoid using non-abbreviated
    prefixes, e.g. `MetaBackend:`, or `meta-backend:`, other prefixes are
    Currently consisting of only a "blacklist".
    
    https://gitlab.gnome.org/GNOME/mutter/merge_requests/519

 .gitlab-ci/check-commit-log.sh | 23 ++++++++++++++++++++++-
 1 file changed, 22 insertions(+), 1 deletion(-)
---
diff --git a/.gitlab-ci/check-commit-log.sh b/.gitlab-ci/check-commit-log.sh
index cc3bcee60..b5e7bae08 100755
--- a/.gitlab-ci/check-commit-log.sh
+++ b/.gitlab-ci/check-commit-log.sh
@@ -23,9 +23,30 @@ function commit_message_has_url() {
   return $?
 }
 
+function commit_message_subject_is_compliant() {
+  commit=$1
+  commit_message_subject=$(git show -s --format='format:%s' $commit)
+
+  if echo "$commit_message_subject" | grep -qe "\(^meta-\|^Meta\)"; then
+    echo " - message subject should not be prefixed with 'meta-' or 'Meta'"
+    return 1
+  fi
+
+  return 0
+}
+
 for commit in $commits; do
+  commit_short=$(echo $commit | cut -c -8)
+
   if ! commit_message_has_url $commit; then
-    echo "Missing merge request or issue URL on commit $(echo $commit | cut -c -8)"
+    echo "Missing merge request or issue URL on commit $commit_short"
+    exit 1
+  fi
+
+  errors=$(commit_message_subject_is_compliant $commit)
+  if [ $? != 0 ]; then
+    echo "Commit message for $commit_short is not compliant:"
+    echo "$errors"
     exit 1
   fi
 done