- If you attempted to get a branch feed on a empty repository, it would
result in a panic as the code expects that the branch exists.
- `context.RepoRefByType` would normally already 404 if the branch
doesn't exist, however if a repository is empty, it would not do this
check.
- Fix bug where `/atom/branch/*` would return a RSS feed.
(cherry picked from commit d27bcd98a41b69e313535e5e91e4272136a4bab1)
(cherry picked from commit c58566403df728c1f71b1dd554a573c011a59d7e)
(cherry picked from commit b8b3f6ab8b)
(cherry picked from commit 195520100b)
(cherry picked from commit 6e417087ddf41e79a146366a5db157c7a76af615)
(cherry picked from commit ff91e5957ac728118cddb06bddd95d32cb4df815)
(cherry picked from commit 6626d5cc75681d3b16b4496a4e0e83a257a3f46a)
(cherry picked from commit 62f8ab793b12251e1793bc14ace95cda76121baa)
(cherry picked from commit e5bbf1a2d060b4ef1324afd8ed9b38e294b3dffb)
(cherry picked from commit f5b8c8edea5d17ba51327684a6e8127ac0f09503)
(cherry picked from commit 50948fa11b9c9ccac9e86dc9943bad71cf189370)
83a9f7f442