How to view file diff in git before commit

Question

This often happens to me:

I'm working on a couple related changes at the same time over the course of a day or two, and when it's time to commit, I end up forgetting what changed in a specific file. (This is just a personal git repo, so I'm ok with having more than one update in a commit.)

Is there any way to preview the changes between my local file, which is about to be checked in, and the last commit for that file?

Something like:

git diff --changed /myfile.txt 

And it would print out something like:

line 23   (last commit): var = 2+2   (current):     var = myfunction() + 2  line 149   (last commit): return var   (current):     return var / 7 

This way, I could quickly see what I had done in that file since it was last checked in.

Answer 1

If you want to see what you haven't git added yet:

git diff myfile.txt 

or if you want to see already added changes

git diff --cached myfile.txt 

Answer 2

git diff HEAD file 

will show you changes you added to your worktree from the last commit. All the changes (staged or not staged) will be shown.