[参考資料]
http://www-creators.com/archives/1272
developブランチを例に。
[1] git fetch origin
全てのブランチをfetch
$ git fetch origin
[1] git fetch origin develop
developブランチのみをfetch
$ git fetch origin develop
[2] git merge --no-ff origin/develop
$ git merge --no-ff origin/develop
[3] git push origin develop
$ git push origin develop