#!/bin/bash

#
# Copyright 2010 David M. Lee, II <leedm777@yahoo.com>
#
# This git update hook compares the author emails from commits with a
# whitelist stored in ${GIT_DIR}/author-whitelist.  If any commit has an
# author that is not whitelisted, the offending author's email is displayed
# then the update is rejected.
#

if test -z ${GIT_DIR}; then
    cat <<EOF >&2
Do not run directly.  This is a git update hook.
EOF
    exit 1
fi

# Prints a list of all authors for the given revlist to stdout
function git-authors
{
    git rev-list --pretty=format:"%ae" "$1" | grep -v "^commit " | sort | uniq
}

function commit-authors
{
    if test "$1" -eq 0000000000000000000000000000000000000000; then
	# creating a new branch.  Unfortunately, we don't know if we're
	# cloning an existing branch or not, so we'll have to check all
	# revisions.  This went pretty quick on an Ubuntu 10.10 VM against
	# the Linux kernel repo (8601 authors, 221706 commits, < 7 seconds).
	# I doubt a performance optimization is necessary.
	git-authors $2
    else
	git-authors $1..$2
    fi
}

# Some things to note when modifying this script
#  * the output from commit-authors can be pretty much anything.  Just clone
#    the Linux kernel repo and look at the authors.  Given that, you
#    _really_ have to be careful about shell injection.
#
#  * the grep below will remove whitelisted authors from the list of
#    commit-authors.  it will return 0 if there are non-whitelisted
#    commit-authors.
#
#  * as a (pleasant) side effect, the list of non-whitelisted authors is
#    printed to stdout.
#
#  * this is surpisingly fast; it took less than 100ms to compare 8601
#    commit-authors against a whitelist of 8601 authors.
commit-authors $2 $3 | \
    grep -v --fixed-strings --file=${GIT_DIR}/author-whitelist

if test $? -eq 0; then
    # all is good
    echo ">>> Non-whitelisted Authors.  Fail!" >&2
    exit 1
fi