How to check if there's nothing to be committed in the current branch?

Question

The goal is to get an unambiguous status that can be evaluated in a shell command.

I tried git status but it always returns 0, even if there are items to commit.

git status
echo $?  #this is always 0

I have an idea but I think it is rather a bad idea.

if [ git status | grep -i -c "[a-z]"> 2 ];
then
 code for change...
else
  code for nothing change...
fi

any other way?

---

update with following solve, see Mark Longair's post

I tried this but it causes a problem.

if [ -z $(git status --porcelain) ];
then
    echo "IT IS CLEAN"
else
    echo "PLEASE COMMIT YOUR CHANGE FIRST!!!"
    echo git status
fi

I get the following error [: ??: binary operator expected

now, I am looking at the man and try the git diff.

===================code for my hope, and hope better answer======================

#if [ `git status | grep -i -c "$"` -lt 3 ];
# change to below code,although the above code is simple, but I think it is not strict logical
if [ `git diff --cached --exit-code HEAD^ > /dev/null && (git ls-files --other --exclude-standard --directory | grep -c -v '/$')` ];
then
        echo "PLEASE COMMIT YOUR CHANGE FIRST!!!"
    exit 1

else
    exit 0
fi

Answer 1

An alternative to testing whether the output of git status --porcelain is empty is to test each condition you care about separately. One might not always care, for example, if there are untracked files in the output of git status.

For example, to see if there are any local unstaged changes, you can look at the return code of:

git diff --exit-code

To check if there are any changes that are staged but not committed, you can use the return code of:

git diff --cached --exit-code

Finally, if you want to know about whether there are any untracked files in your working tree that aren't ignored, you can test whether the output of the following command is empty:

git ls-files --other --exclude-standard --directory

Update: You ask below whether you can change that command to exclude the directories in the output. You can exclude empty directories by adding --no-empty-directory, but to exclude all directories in that output I think you'll have to filter the output, such as with:

git ls-files --other --exclude-standard --directory | egrep -v '/$'

The -v to egrep means to only output lines that don't match the pattern, and the pattern matches any line that ends with a /.