撤销修改：git checkout -- filename ；将工作区文件回到最近一次add 或者 commit的状态
撤销修改分为三种情况：
1、未提交至暂存区
使用git checkout -- filename 将master的文件替换到工作区
2、已提交至暂存区
① 使用git reset HEAD filename 撤销暂存区的修改，恢复暂存区的文件与master分支一致
② 再使用git checkout -- filename 将暂存区的文件替换到工作区
3、已提交至master分支
① 使用git reset --hard commit-id 回退版本至修改前
② 使用git checkout -- filename 将master分支文件替换到工作区
D:\learn\git_test>git checkout -- readme.txt
删除文件：git rm filename
D:\learn\git_test>git status
On branch master
Changes not staged for commit:
(use "git add/rm <file>..." to update what will be committed)
(use "git checkout -- <file>..." to discard changes in working directory)
deleted: readme.txt
Untracked files:
(use "git add <file>..." to include in what will be committed)
git
type
no changes added to commit (use "git add" and/or "git commit -a")
D:\learn\git_test>git rm readme.txt
rm 'readme.txt'
D:\learn\git_test>git status
On branch master
Changes to be committed:
(use "git reset HEAD <file>..." to unstage)
deleted: readme.txt
Untracked files:
(use "git add <file>..." to include in what will be committed)
git
type
D:\learn\git_test>git commited -m "delete a file"
git: 'commited' is not a git command. See 'git --help'.
The most similar command is
commit-tree
D:\learn\git_test>git commit -m "delete a file"
[master 8b89ced] delete a file
file changed, deletions(-)
delete mode readme.txt
D:\learn\git_test>git status
On branch master
Untracked files:
(use "git add <file>..." to include in what will be committed)
git
type
nothing added to commit but untracked files present (use "git add" to track)
D:\learn\git_test>
若想撤销删除，则也可使用git checkout -- filename 将版本库中文件替换到工作区