Using git hooks to automate tests

We have the flake8, pylint and unit tests automated with Cirrus it's useful to automatically check each commit before allowing it into the tree. Git provides hooks that allow a script to run before a commit takes place and that can reject the commit by exiting with failure. See man 5 githooks for more information.

To enable a simple hook that runs flake8, pylint and unit tests add a file at .git/hooks/pre-commit with the following content:

$ cat .git/hooks/pre-commit
#!/bin/bash

fail () {
    echo "$@: [FAILED]"
    exit 1
}

if git rev-parse --verify HEAD >/dev/null 2>&1
then
        against=HEAD
else
        # Initial commit: diff against an empty tree object
        against=4b825dc642cb6eb9a060e54bf8d69288fbee4904
fi

echo "Check flake8 conformance"
tox -e flake8 || fail flake8
echo "Check pylint conformance"
tox -e pylint || fail pylint
echo "checking unit test suite (py3)"
tox -e unit_tests || fail unit_tests

# If there are whitespace errors, print the offending file names and fail.
exec git diff-index --check --cached $against --

A failure in any of the tests will cause the commit to be rejected. Fix the problem, update the index and try again.

For current Fedora and Ubuntu systems you should have the tox package installed to be able to run the suite.

Other distributions may use different package and command names: consult your distribution's Python documentation for details.