checkout是本地命令

git-checkout - Checkout a branch or paths to the working tree

git 不需要联网就可以使用,你的理解是对的

git checkout -f 我测试了下，结果是这样的

rails@1hao:~/tmp/tmp$ git branch 
* hello
  master
rails@1hao:~/tmp/tmp$ git checkout -f 
rails@1hao:~/tmp/tmp$ git branch 
* hello
  master

另外 git-checkout man手册里是这样说的

 -f, --force
           When switching branches, proceed even if the index or the working tree differs from HEAD. This is used to throw away local changes.

改了文件，加了个文件测试了下

rails@1hao:~/tmp/tmp$ git status
# On branch hello
# Changes to be committed:
#   (use "git reset HEAD <file>..." to unstage)
#
#   new file:   b
#
# 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:   a
#
# Untracked files:
#   (use "git add <file>..." to include in what will be committed)
#
#   c
rails@1hao:~/tmp/tmp$ git checkout -f 
rails@1hao:~/tmp/tmp$ git status 
# On branch hello
# Untracked files:
#   (use "git add <file>..." to include in what will be committed)
#
#   c
nothing added to commit but untracked files present (use "git add" to track)

那些更改的和添加到缓存区的文件都没有了