Determining if a directory has changed since the last Git commit

Sometimes it can be useful to determine if a specific directory has changed since the last Git commit.

This can be achieved with the following bash command:

DIRECTORY=mydir
if [[ -z $(git diff HEAD~1 -- $DIRECTORY) ]]; then echo "Directory changed"; else echo "Directory not changed"; fi

This works by running a Git diff between the current HEAD and the parent commit. If any files in the specified directory have changed then the diff command will return 0, else it will return 1.

You can also easily modify this to run logic only if the directory has not changed:

if [[ -z $(git diff HEAD~1 -- $DIRECTORY) ]]; then echo "Directory has not changed"; fi

Or only if the directory has changed:

if [[ $(git diff HEAD~1 -- $DIRECTORY) ]]; then echo "Directory has not changed"; fi

My particular use case was for selectively cancelling CI/CD tests. The CI/CD runner I was using only supported triggers based on files changed between the current master HEAD and the change commit, but I needed to calculate the diff between the current commit and its parent.