我已经运行了git status命令并且
# On branch master
# Your branch is ahead of 'origin/master' by 4 commits.
# (use "git push" to publish your local commits)
#
# Changes not staged for commit:
# (use "git add <file>..." to update what will be committed)
# (use "git checkout -- <file>..." to discard changes in working directory)
#
# modified: app/views/layouts/_header.html.erb
#
no changes added to commit (use "git add" and/or "git commit -a")
在提交到远程仓库之前,我想撤销所有的4个提交和未暂存的更改。我该怎么做?