git-word-diff-auto - offers a missing --word-diff="auto"

git-word-diff-auto

#!/bin/sh
#
# git-word-diff-auto - offers a missing --word-diff="auto"
#
# Copyright (c) 2012 Akinori MUSHA
#
# All rights reserved.
#
# Redistribution and use in source and binary forms, with or without
# modification, are permitted provided that the following conditions
# are met:
# 1. Redistributions of source code must retain the above copyright
#    notice, this list of conditions and the following disclaimer.
# 2. Redistributions in binary form must reproduce the above copyright
#    notice, this list of conditions and the following disclaimer in the
#    documentation and/or other materials provided with the distribution.
#
# THIS SOFTWARE IS PROVIDED BY THE AUTHOR AND CONTRIBUTORS ``AS IS'' AND
# ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE
# IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE
# ARE DISCLAIMED.  IN NO EVENT SHALL THE AUTHOR OR CONTRIBUTORS BE LIABLE
# FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL
# DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS
# OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION)
# HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT
# LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY
# OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF
# SUCH DAMAGE.
#

usage () {
    cat <<EOF >&2
usage: $0 <git-subcommand> <args>..

`basename $0` runs a given subcommand with a --word-diff option
enabling colorization if stdout is a tty.  It can be used to build an
alias.

e.g.
    git config --global alias.wdi 'word-diff-auto diff'
    git config --global alias.wdc 'word-diff-auto diff --cached'

The following configuration variables are recognized.

    color.wordDiff.old
        The color used for highlighting removed words.
        (default: "red reverse")

    color.wordDiff.new
        The color used for highlighting added words.
        (default: "green reverse")
EOF
}

main () {
    local opt OPTIND=1

    while getopts '' opt; do
        :
    done

    shift $(($OPTIND - 1))

    if [ $# -eq 0 ]; then
        usage
        exit 1
    fi

    local command="$1" slot color; shift

    if git config --get-colorbool color.diff; then
        set -- "$command" --word-diff=color "$@"
        for slot in old new; do
            eval "color=\`word_color $slot\`"
            set -- -c color.diff.$slot="$color" "$@"
        done
    else
        set -- "$command" --word-diff "$@"
    fi

    exec git "$@"
}

word_color () {
    local slot="$1" color
    case "$slot" in
        old) default="red reverse" ;;
        new) default="green reverse" ;;
        *)   return ;;
    esac
    color="$(git config --get diff.wordDiff.$slot)"
    echo "${color:-$default}"
}

main "$@"