git: Why doesn't git diff show any differences?

问题

If I run 'git status' on my repo it gives:

# On branch master
# Changes to be committed:
#   (use "git reset HEAD <file>..." to unstage)
#
#   modified: myfile

However, if I do a 'git diff myfile' it shows no differences. Is this because I have made a change and removed it so it is back to the original?

Should I run 'git checkout myfile' to clear it?

回答1:

Your file is already staged to be committed. You can show it's diff using the --cached option of git.

git diff --cached myfile

To unstage it, just do what git status suggests in it's output ;)

You can check The Git Index For more info.

回答2:

I have a preference for the --staged alias, mostly because I find that --staged actually means what I want to do, i.e. show me the staged differences.

git diff --staged

The accepted answer is correct and I have no qualms with it. Just personally think that --cached feels like git diff is caching the answer and showing me pre-calculated results or something.

I also like git diff HEAD because it's a more general. It puts together two concepts that most folks know, that is:

1. git diff <commit> allows you to see the difference between your current position and a previous commit.

2. HEAD (or head because holding shift is annoying) is a reference to the tip of your branch. (For those of you who are counting keystrokes, @ is an alias for HEAD.)

Combined, these two generally useful concepts result in:

git diff head
git diff @

回答3:

For Staging Area vs Repository comparison use

$git diff --staged

For Working vs Repository comparison use

$ git diff 

but if a file is changed and added to staging area ($ git add fileName) and we try to see the difference with ( $ git diff). It will not return any difference since the file is in staging area and it will not be compared with the repository.

来源：https://stackoverflow.com/questions/4734844/git-why-doesnt-git-diff-show-any-differences