Always squash MRs created by Housekeeper

gems/gitlab-housekeeper/lib/gitlab/housekeeper/gitlab_client.rb

@@ -153,7 +153,8 @@ def create_merge_request(
           target_project_id: target_project_id,
           remove_source_branch: true,
           assignee_ids: usernames_to_ids(change.assignees),
-          reviewer_ids: usernames_to_ids(change.reviewers)
+          reviewer_ids: usernames_to_ids(change.reviewers),
+          squash: true
         })
       end
 

gems/gitlab-housekeeper/lib/gitlab/housekeeper/runner.rb

@@ -124,7 +124,8 @@ def require_keeps
       end
 
       def print_change_details(change, branch_name)
-        base_message = "Merge request URL: #{change.mr_web_url || '(known after create)'}, on branch #{branch_name}."
+        base_message = "Merge request URL: #{change.mr_web_url || '(known after create)'}, on branch #{branch_name}. " \
+                       "Squash commits enabled."
         base_message << " CI skipped." if change.push_options.ci_skip
 
         @logger.puts base_message.yellowish

gems/gitlab-housekeeper/spec/gitlab/housekeeper/gitlab_client_spec.rb

@@ -343,7 +343,8 @@
             target_project_id: 456,
             remove_source_branch: true,
             assignee_ids: [assignee_id],
-            reviewer_ids: [reviewer_id]
+            reviewer_ids: [reviewer_id],
+            squash: true
           },
           headers: {
             'Content-Type' => 'application/json',