GitLab Shell如何通过SSH工作

GitLab访问Git仓库

首先回顾GitLab的Git仓库四种访问方式：

git pull over http -> gitlab-rails (Authorization) -> accept or decline -> execute git command
git push over http -> gitlab-rails (git command is not executed yet) -> execute git command -> gitlab-shell pre-receive hook -> API call to gitlab-rails (authorization) -> accept or decline push
git pull over ssh -> gitlab-shell -> API call to gitlab-rails (Authorization) -> accept or decline -> execute git command
git push over ssh -> gitlab-shell (git command is not executed yet) -> execute git command -> gitlab-shell pre-receive hook -> API call to gitlab-rails (authorization) -> accept or decline push

四种方式都有GitLab Shell的参与，但不同过程GitLab Shell发挥了不同的作用，并且它并不是一个整体的服务，而是由一些子命令组合而成。HTTP方式的Git操作，经gitlab workhorse直接交由Rails应用处理，然后通过HTTP协议交换数据，对于git的操作有三条路径：Gem包Rugged、Raw Git命令或者Gitaly，push/pull一般只跟后两种有关，GitLab Shell充当的作用仅仅是git hook的作用。