Determine if Git working directory is clean from a script

Parsing the output of git status is a bad idea because the output is intended to be human readable, not machine-readable. There's no guarantee that the output will remain the same in future versions of Git or in differently configured environments.

UVVs comment is on the right track, but unfortunately the return code of git status doesn't change when there are uncommitted changes. It does, however, provide the --porcelain option, which causes the output of git status --porcelain to be formatted in an easy-to-parse format for scripts, and will remain stable across Git versions and regardless of user configuration.

We can use empty output of git status --porcelain as an indicator that there are no changes to be committed:

if [ -z "$(git status --porcelain)" ]; then 
  # Working directory clean
else 
  # Uncommitted changes
fi

If we do not care about untracked files in the working directory, we can use the --untracked-files=no option to disregard those:

if [ -z "$(git status --untracked-files=no --porcelain)" ]; then 
  # Working directory clean excluding untracked files
else 
  # Uncommitted changes in tracked files
fi

To make this more robust against conditions which actually cause git status to fail without output to stdout, we can refine the check to:

if output=$(git status --porcelain) && [ -z "$output" ]; then
  # Working directory clean
else 
  # Uncommitted changes
fi

It's also worth noting that, although git status does not give meaningful exit code when the working directory is unclean, git diff provides the --exit-code option, which makes it behave similar to the diff utility, that is, exiting with status 1 when there were differences and 0 when none were found.

Using this, we can check for unstaged changes with:

git diff --exit-code

and staged, but not committed changes with:

git diff --cached --exit-code

Although git diff can report on untracked files in submodules via appropriate arguments to --ignore-submodules, unfortunately it seems that there is no way to have it report on untracked files in the actual working directory. If untracked files in the working directory are relevant, git status --porcelain is probably the best bet.

Use:

git diff-index --quiet HEAD

The return code reflects the state of the working directory (0 = clean, 1 = dirty). Untracked files are ignored.