clang-format pre-commit hook

pre-commit

#!/bin/sh

# Check if this is the initial commit
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

# Check if it parses the clang-format style
git diff --staged --submodule=diff -U0 --no-color $against | clang-format-diff -p1 > .clang-format.diff
if [ -s .clang-format.diff ]; then
    echo "clang-format style violation:\n"
    cat .clang-format.diff
    exit_code=1
else
    exit_code=0
fi

rm .clang-format.diff
exit $exit_code