WIP: UX re-design branch items with flexbox
EE port of gitlab-org/gitlab-ce!17832
Replaces !5021 (merged), whose source branch was not in https://gitlab.com/gitlab-org/gitlab-ee but in https://gitlab.com/tnir/gitlab-ee
Edited by Takuya Noguchi
EE port of gitlab-org/gitlab-ce!17832
Replaces !5021 (merged), whose source branch was not in https://gitlab.com/gitlab-org/gitlab-ee but in https://gitlab.com/tnir/gitlab-ee