.git_pre-commit

#!/bin/sh

# create symlink to your hook directory with (from project dir)
# ln -s ../../.git_pre-commit .git/hooks/pre-commit


. git-sh-setup  # for die 
if git-diff-index -p -M --cached HEAD -- \
| grep '^+' \
| grep 'USE_EXPERIMENT= *"Y"'; then
    die Blocking commit because of banned string
fi