git-blamed-diff

#!/bin/sh -e
# SPDX-License-Identifier: WTFPL

tmpa=
tmpb=

cleanup () {
    rm -f "$tmpa" "$tmpb"
}

blame () {
    # sed to remove git-blame's obnoxious line numbers
    git blame -s "$@" | sed 's/[[:digit:]]*)//'
}

case $# in
    1)
        arev=HEAD
        brev=
        ;;
    2)
        arev="$2^"
        brev="$2"
        ;;
    *)
        cat >&2 <<- EOF
		usage: git blamed-diff FILE [REV]
		Prints diff of FILE between REV and REV~, annotating lines with commit info.
		If REV isn't specified, the diff between working directory and HEAD is used.
	EOF
        exit 1
	;;
esac

trap cleanup EXIT

tmpa=$(mktemp blame.XXXXXX)
tmpb=$(mktemp blame.XXXXXX)

blame "$1" "$arev" > "$tmpa"
# $brev should not be quoted
# if it's empty, it should not take one argument
blame "$1" $brev > "$tmpb"

# -w to ignore git-blame's pesky alignment
diff -w -u "$tmpa" "$tmpb"  \
     --label "$arev" --label "${brev:-working directory}" || exit 0