Use merge strategy that wil always prefer branch we're marking as STABLE/TESTING.

The problem is in fact that not all branches are merged together and it
usually causes conflicts on version string (documentation, config,
changelog,...). By simply using branch we're merging to STABLE/TESTING
we will get the correct merge.

scripts/create-release.sh

@@ -44,7 +44,7 @@ mark_as_release() {
     echo "* Marking release as $rel_branch"
     ensure_local_branch $rel_branch
     git checkout $rel_branch
-    git merge $branch
+    git merge -s recursive -X theirs $branch
 }
 
 # Read required parameters