pre-commit

#!/bin/sh
#
# Called by "git commit" with no arguments.  The hook should
# exit with non-zero status after issuing an appropriate message if
# it wants to stop the commit.

set -e

git diff --cached | while IFS= read -r line
do
read -r -a WORDS <<< "$line"
diff=${line:0:1}
case ${WORDS[0]} in
    diff)
        file=${WORDS[2]:2}
        ;;
    new | index | deleted | similarity | rename | --- | +++)
        ;;
    @@)
        state=0
        ;;
    *)
        case ${diff} in
            -)
                case ${state} in
                    0 | 1)
                        state=1
                        ;;
                    2)
                        state=4
                        ;;
                    *)
                        echo >& too many changes in ${file}
                        exit 1
                        ;;
                esac
                ;;
            +)
                case ${state} in
                    0 | 2)
                        state=2
                        ;;
                    1 | 3)
                        state=3
                        ;;
                    *)
                        echo >&2 too many changes in ${file}
                        exit 1
                        ;;
                esac
                ;;
            ' ')
                # unchanged line
                state=0
                ;;
            *)
                echo >&2 "parse error on '${line}' in ${file}"
                exit 2
                ;;
        esac
        ;;
esac
done