我不小心挥动回到主分支，同时操纵铁路tutoial。现在我无法回来。下面是我的终端输出，包括thistake和后来尝试返回分支机构。没有一个工作
owen358:~/workspace $ cd sample_app #<-- cd into "user-microposts" branch
owen358:~/workspace/sample_app (user-microposts) $ cd sample_app #<--accidentally did same command and went back into master branch
owen358:~/workspace/sample_app/sample_app (master) $ cd sample_app
bash: cd: sample_app: No such file or directory
owen358:~/workspace/sample_app/sample_app (master) $ git branch #<-- this command supposed to list all branches but did nothing
owen358:~/workspace/sample_app/sample_app (master) $ git checkout user-microposts #<-- my attempt to return to user-microposts branch
error: pathspec 'user-microposts' did not match any file(s) known to git.
owen358:~/workspace/sample_app/sample_app (master) $ git branch
owen358:~/workspace/sample_app/sample_app (master) $ git show-branch #<-- another way i found that is supposed to list all the branches and didnt work
No revs to be shown.
owen358:~/workspace/sample_app/sample_app (master) $
我怎样才能回到我正在处理的user-microposts分支，为什么我的命令什么都不做呢？