How can I check in a Bash script if my local Git repository has changes?

There are some scripts that do not work correctly if they check for changes.

I tried it like this:

VN=$(git describe --abbrev=7 HEAD 2>/dev/null)

git update-index -q --refresh
CHANGED=$(git diff-index --name-only HEAD --)
if [ ! -z $CHANGED ];
    then VN="$VN-mod"
fi

Is there some kind of boolean check if there has been changes since the last commit, or how can I really test if there are new changes to my local repository?

I'm doing all this for a version creation script (that I found somewhere here).

Solution 1:

Using git status:

cd /git/directory
if [[ `git status --porcelain` ]]; then
  # Changes
else
  # No changes
fi

Solution 2:

What you're doing will almost work: you should quote $CHANGED in case it's empty, and -z tests for empty, which means no changes. What you meant was:

if [ -n "$CHANGED" ]; then
    VN="$VN-mod"
fi

A quote from Git's GIT-VERSION-GEN:

git update-index -q --refresh
test -z "$(git diff-index --name-only HEAD --)" ||
VN="$VN-dirty"

It looks like you were copying that, but you just forgot that detail of quoting.

Of course, you could also just do this:

if git diff-index --quiet HEAD --; then
    # No changes
else
    # Changes
fi

Or if you only care about the "something has changed" case:

if ! git diff-index --quiet HEAD --; then
    VN="$VN-mod"
fi

Using --quiet has the benefit that Git can stop processing as soon as it encounters a single diff, so it may not have to check your entire work tree.