How do i see the differences in git files?

giraffelife

Let's say i made a change to a file called README.md in my git repository by adding a new line, and I do a git status.

$ git status
On branch master
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:   README.md

no changes added to commit (use "git add" and/or "git commit -a")

Now I want to see what is different between what I have previously commit with README.md and what I just modified, because I may not want to keep the modified copy. Run a git diff, this shows me the diff between what is commited with README.md and what I've just modified. I added the forth line.

$ git diff 
diff --git a/README.md b/README.md
index 1408e61..4ba7d0a 100644
--- a/README.md
+++ b/README.md
@@ -3,3 +3,5 @@ First Line: Today i woke up and went running
 Second Line: When I get back from running I'm tired
 
 Third Line: I got straight to bed
+
+Fourth Line: and I dream of running the marathon

If you want to keep the changes, just do a git add <file>, git commit -m "<your message>", as before