git - Refresh staged files

Question

In git, is there any (simple) way to modify the index so that only changes to files which are already in it are added? It sounds kind of complicated, but what I want to achieve is simple.

Lets say my index looks like this (slightly stripped git status output):

# Changes to be committed:
#       modified:   A
#       modified:   B
#
# Changed but not updated:
#       modified:   B
#       modified:   C
#
# Untracked files:
#       D

Some changes to B are in the index, some aren't. C is not staged at all.

How can I update B in the index (stage its unstaged changes) without adding C?

I.e. I would like for the index to look like this:

# Changes to be committed:
#       modified:   A
#       modified:   B
#
# Changed but not updated:
#       modified:   C
#
# Untracked files:
#       D

In this simple case it can of course be achieved with a simple git add B, but I would like to know if there's a simple answer for the general case. I tried git add --refresh, but if I understand correctly, that only updates stat info.

Answer 1

以下命令将更新索引以包含 B 中尚未暂存的其他更改：

git update-index --again

Answer 2

我不知道这样做的完全微不足道的方法，但是：

git status --porcelain

将文件 B（并且只有 B）显示为状态“MM”，因此：

git status --porcelain | grep ^MM | cut -d' ' -f 2

将生成此类文件的列表。

不过，“重新添加”A 并没有什么坏处。

您也可以使用git diff-index --cached --name-status HEAD. （如果你的 git 太老了，可能需要这个git status --porcelain。）

Answer 3

而不是--refresh，你应该使用--update：

git add --update

在此之后，git status应该看起来像：

# Changes to be committed:
#       modified:   A
#       modified:   B
#       modified:   C
#
# Untracked files:
#       D