Group download buttons in a .btn-group

app/views/projects/buttons/_download_links.html.haml

 - formats = [['zip', 'btn-primary'], ['tar.gz'], ['tar.bz2'], ['tar']]
 
-.d-flex.justify-content-between
+.btn-group.ml-0.w-100
   - formats.each do |(fmt, extra_class)|
     = link_to fmt, project_archive_path(project, id: tree_join(ref, archive_prefix), path: path, format: fmt), rel: 'nofollow', download: '', class: "btn btn-xs #{extra_class}"

changelogs/unreleased/61880-download-btn-group.yml

+---
+title: Group download buttons into a .btn-group
+merge_request:
+author:
+type: other