有时git会建议git rm——cached来取消文件，有时git会重置HEAD文件。什么时候用哪个?
D:\code\gt2>git init
Initialized empty Git repository in D:/code/gt2/.git/
D:\code\gt2>touch a
D:\code\gt2>git status
# On branch master
#
# Initial commit
#
# Untracked files:
# (use "git add <file>..." to include in what will be committed)
#
# a
nothing added to commit but untracked files present (use "git add" to track)
D:\code\gt2>git add a
D:\code\gt2>git status
# On branch master
#
# Initial commit
#
# Changes to be committed:
# (use "git rm --cached <file>..." to unstage)
#
# new file: a
#
D:\code\gt2>git commit -m a
[master (root-commit) c271e05] a
0 files changed, 0 insertions(+), 0 deletions(-)
create mode 100644 a
D:\code\gt2>touch b
D:\code\gt2>git status
# On branch master
# Untracked files:
# (use "git add <file>..." to include in what will be committed)
#
# b
nothing added to commit but untracked files present (use "git add" to track)
D:\code\gt2>git add b
D:\code\gt2>git status
# On branch master
# Changes to be committed:
# (use "git reset HEAD <file>..." to unstage)
#
# new file: b
#
Git rm——cached用于从索引中删除文件。在文件已经在repo的情况下，git rm——cached将从索引中删除该文件，将其留在工作目录中，现在提交也将从repo中删除该文件。基本上，在提交之后，您将取消该文件的版本控制，并保留一个本地副本。
git重置HEAD文件(默认使用——mixed标志)的不同之处在于，在文件已经在repo的情况下，它会用repo (HEAD)中的索引版本替换文件的索引版本，有效地取消对它的修改。
在未版本化文件的情况下，它将取消整个文件，因为该文件不在HEAD中。在这方面，git reset HEAD file和git rm——cached是一样的，但它们是不一样的(就像已经在repo中的文件一样)
对于为什么在git中有两种方法取消文件的问题?-在git中从来没有真正只有一种方法来做任何事情。这就是它的美妙之处:)
这个线程有点老了，但我仍然想添加一个小演示，因为它仍然不是一个直观的问题:
me$ git status
# On branch master
# Changes to be committed:
# (use "git reset HEAD <file>..." to unstage)
#
# new file: to-be-added
# modified: to-be-modified
# deleted: to-be-removed
#
me$ git reset -q HEAD to-be-added
# ok
me$ git reset -q HEAD to-be-modified
# ok
me$ git reset -q HEAD to-be-removed
# ok
# or alternatively:
me$ git reset -q HEAD to-be-added to-be-removed to-be-modified
# ok
me$ 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)
#
# modified: to-be-modified
# deleted: to-be-removed
#
# Untracked files:
# (use "git add <file>..." to include in what will be committed)
#
# to-be-added
no changes added to commit (use "git add" and/or "git commit -a")
git reset HEAD(不带-q)给出关于修改文件的警告，其退出码为1，这将被视为脚本中的错误。
Edit: git签出要修改要删除的HEAD也适用于取消暂存，但会将更改完全从工作空间中删除
更新git 2.23.0:命令会不时发生变化。现在，git状态显示:
(use "git restore --staged <file>..." to unstage)
．.． 哪种对这三种变化都有效
