#!/bin/sh

NULL_HASH='0000000000000000000000000000000000000000'

commit_range() {
    local old_rev=$1
    local new_rev=$2

    case $NULL_HASH in
        $new_rev) return ;;
        $old_rev) git rev-list --reverse $new_rev --not --all ;;
        *) git rev-list --reverse $old_rev..$new_rev ;;
    esac
}

is_binary() {
    # perl -e '$/ = undef; exit 1 if (<> =~ /\x00/)'
    # hexdump -b | grep -q -w 000

    hexdump -e '1/1 "%02x""\n"' | grep -qF 00
}

changed_files() {
    commit=$1

    root=""
    if ! git rev-parse --quiet --verify $commit~ >/dev/null
    then
        root="--root"
    fi

    git diff-tree --name-only --format= --diff-filter=bdx $root $commit
}

check_for_binary_files() {
    local commit=$1
    local ref_name=$2
    
    local files=$(changed_files $commit)

    for file in $files
    do
        if git show $commit:"$file" | head -c1024 | is_binary
        then
            echo "File '$file' contains binary content, rejected"
            echo "Offending commit: $commit in ref '$ref_name'"
        fi
    done
     
}

while read old_rev new_rev ref_name
do
    commits=$(commit_range $old_rev $new_rev)

    for commit in $commits
    do
        check_for_binary_files $commit $ref_name || exit 1
    done
        
done

exit 1