Here’s a few tips for using a Git pre-commit hook.
Keep your hook script in source control
Commit your hook script (say
pre-commit.sh) at the root of your
project and include the installation instructions in your
README/documentation to encourage all developers use it.
Installation is nothing more than:
ln -s ../../pre-commit.sh .git/hooks/pre-commit
Then everyone benefits from running the same set of tests before committing and updates are picked up automatically.
Stash unstaged changes before running tests
Ensure that code that isn’t part of the prospective commit isn’t tested
within your pre-commit script. This is missed by many sample pre-commit
scripts but is easily achieved with
# pre-commit.sh STASH_NAME="pre-commit-$(date +%s)" git stash save -q --keep-index $STASH_NAME # Test prospective commit ... STASHES=$(git stash list) if [[ $STASHES == "$STASH_NAME" ]]; then git stash pop -q fi
-q flags specify quiet mode.
Run your test suite before each commit
It’s best to have a script (say
run_tests.sh) that encapsulates the
standard arguments to your test runner so your pre-commit script doesn’t
fall out of date. Something like:
# pre-commit.sh git stash -q --keep-index ./run_tests.sh RESULT=$? git stash pop -q [ $RESULT -ne 0 ] && exit 1 exit 0
where a sample
run_tests.sh implementation for a Django project may
# run_tests.sh ./manage.py test --settings=settings_test -v 2
Skip the pre-commit hook sometimes
Be aware of the
--no-verify option to
git commit. This bypasses the
pre-commit hook when committing, which is useful if you have just
manually run your test suite and don’t need to see it run again when
I use git aliases to make this easy:
# ~/.bash_aliases alias gc='git commit' alias gcv='git commit --no-verify'
Search yo.. code for debugging code
At some point, someone will try and commit a file containing
import pdb; pdb.set_trace()
or some other debugging code. This can be easily avoided using the
pre-commit.sh file to grep the staged codebase and abort the commit if
forbidden strings are found.
Here’s an example that looks for
FILES_PATTERN='\.(js|coffee)(\..+)?$' FORBIDDEN='console.log' git diff --cached --name-only | \ grep -E $FILES_PATTERN | \ GREP_COLOR='4;5;37;41' xargs grep --color --with-filename -n $FORBIDDEN && echo 'COMMIT REJECTED Found "$FORBIDDEN" references. Please remove them before commiting' && exit 1
It’s straightforward to extend this code block to search for other terms.