git pre-push hook

This article introduces git pre-push hook.

Problem

In Lean project, we use a modified version of Google’s C++ style checker. I want to automatically run the checker over the changed files before I push commits to git repositories. This is useful because it prevents me from accidentally pushing the commits which contain style problems.

Solution: git pre-push hook

Since git 1.8.2, git introduced pre-push hook which is executed before actual push operation is performed. The following two steps solve the problem.

• Create <PROJECT_ROOT>/.git/hooks/pre-push file with the following contents:

#!/usr/bin/env bash
IFS=' '
DIR="$( cd "$( dirname "$0" )" && pwd )"
CHECKER=$DIR/../../src/cmake/Modules/cpplint.py
while read local_ref local_sha remote_ref remote_sha;
do
    CHANGED_FILES=`git diff --name-only $local_sha $remote_sha | grep '(cpp|h)$'`
    if [ ! -z "$CHANGED_FILES" -a "$CHANGED_FILES" != " " ]; then
        echo $CHANGED_FILES | xargs $CHECKER
        RET=$?
        if [ $RET -ne 0 ]; then
            echo "There is error(s) from style-check. Please fix them before push to the repo."
            exit $RET
        fi
    fi
done
exit 0

• Give “exec” permission to the file

chmod +x <PROJECT_ROOT>/.git/hooks/pre-push

Note that you need to change CHECKER variable if you want to use other checkers.