run-a-command-if-there-are-unstaged-changes.md

Run a command if there are unstaged changes

A quick one-liner to run a command only if there are unstaged changes: the --quiet flag of git diff. The flag does two things:

1. disables all output of the command, and
2. exits with 1 if there are differences, and 0 if there are no differences

That means you can combine it with boolean operators to only run another command if files have (or have not) changed:

# run `somecommand` if there are unstaged changes
git diff --quiet || somecommand

# run `somecommand` if there are unstaged changes
git diff --quiet && somecommand

Note that this only works for unstaged changes in files that git already tracks; new files and changes staged with git add are not counted.

Note too that because an exit code of 0 indicates success and anything else indicates failure, the boolean operators' usual behavior is flipped: && only evaluates the right side if the left is 0, and || only evaluates the right side if the left is not 0.