My git pre-commit hook

pre-commit.sh

#!/bin/bash

# Git pre-commit hook
#####################
#
# - check for whitespace problems (trailing spaces, ...)
# - check for lines with 'FIXME'
# - running tests
# - running code style check (pep8) on modified files
# - designed for Windows, for Linux replace `> NUL` with `> /dev/null`

########################################################################
# Check, if any changes have been made

changes_count=$(git diff --cached | wc -l)

if [ "$changes_count" -ne "0" ]; then

    ########################################################################
    # Check for whitespace errors
    git diff --cached --check  # Check for whitespace errors

    code=$?

    if [ "$code" -ne "0" ]; then
        echo
        echo "Your changes introduced whitespace errors!"
        exit $code
    fi;
    ########################################################################
    # Check for 'FIXME' lines
    todo_lines=$(git diff --cached | grep ^+ | grep -v pre-commit | grep FIXME | sed 's_^+\s*__g')

    if [ "$todo_lines" != "" ]; then
        echo "You probably didn't want to commit these lines:"
        echo -e "$todo_lines"
        exit 1
    fi

    ########################################################################
    # Run tests

    old_stash=$(git rev-parse -q --verify refs/stash)
    git stash save -q --keep-index
    new_stash=$(git rev-parse -q --verify refs/stash)

    if [ "$old_stash" != "$new_stash" ]; then
        # Python 2
        echo "Running tests... (Python 2)"
        py.test --color yes
        code=$?

        if [ "$code" -eq "0" ]; then
            echo
            echo
            echo "All tests passed. Continuing..."
            echo
        else
            echo
            echo
            echo "Please (re)check tests!"
        fi;

        if [ "$code" -ne "0" ]; then
            git stash pop -q
            exit $code
        fi;

        # Python 3
        echo "Running tests... (Python 3)"
        py.test-3.4 --color yes
        code=$?

        if [ "$code" -eq "0" ]; then
            echo
            echo
            echo "All tests passed. Continuing..."
            echo
        else
            echo
            echo
            echo "Please (re)check tests!"
        fi;


        if [ "$code" -ne "0" ]; then
            git stash pop -q
            exit $code
        fi;

    else
        echo "No changes to test"
        exit 0
    fi

    ########################################################################
    # Run code style check
    echo "Running code style check..."

    modified_files=$(git diff --cached --name-status | grep -v ^D | awk '$1 $2 { print $2}' | grep -e .py$)
    if [ -n "$modified_files" ]; then
        pep8 -r $modified_files
    fi

    git stash pop -q

    if [ "$?" -eq "0" ]; then
        echo
        echo
        echo "Code style is okay. Continuing..."
    else
        echo
        echo
        echo "Please consider cleaning up your code!"
        sleep 5
    fi;
fi;