I 'm confused by the output of git diff
echo "hello">>welcome.txt git diff Why there is no output?
git add welcome.txt git diff Why there is no output?
git diff --cached diff --git a/welcome.txt b/welcome.txt new file mode 100644 index 0000000..ce01362 --- /dev/null +++ b/welcome.txt @@ -0,0 +1 @@ +hello Why it output now?
It seems that git diff don't work without a parameter --cached, is it?
Scenario 1:
echo "hello">>welcome.txt git diff The reason for the confusion is mostly that you're creating a new file that's not already in git. Here the file welcome.txt is not in the git repository so git doesn't know anything about it's history. If there had been a previous version of welcome.txt that was committed you would see differences in this case.
Scenario 2:
git add welcome.txt git diff In this case you've added the file to the staging area. As far as git diff is concerned this effectively commits the file and git diff will only show you differences between the working copy and the version of welcome.txt in the staging area.
Scenario 3:
As you saw it's not quite true that staging a file is the same as committing it as far as git diff is concerned. You can still pass --cached and you will see the differences between the staging area and the current HEAD.
As Simon said it's mostly about the how git diff interacts with the staging area. Pro Git is Also an excellent online resource for getting started with git.
Edit: Git book entry on treeishes.
git diff two treeishes (see link I added to my answer) to diff arbitrary commits, without arguments the default is <staging area or HEAD> <working-copy>. With one argument the second default is the working copy.git diff HEAD will also show differences between the working copy and HEAD. git diff --cached will only show differences between the staging area and HEAD.For this purpose, git add has two meanings:
So when you git diff just after creating the file, you don't see anything. Then when you add it, since it is also directly stagged, you don't see it with git diff but you see it with git diff --cached.
git diff man page says (first entry, without any optional arguments) "This form is to view the changes you made [in your work dir] relative to the index (staging area ..)", hence Simon's informative answer.No, it's all about the staging area. Read more here http://gitready.com/beginner/2009/01/18/the-staging-area.html
