Diff previous revision of file, against current version, with Git

git_difftool_prev_version.sh

#!/usr/bin/env bash

set -o errexit
set -o nounset
set -o pipefail
#set -o xtrace

# The purpose of this script is to show the previous revision of a file, using git difftool

# Get the file in question.
readonly file_path=$1

# Set up our variable, our initial array and our final array.
sha=""
shas=$(git --no-pager log --pretty=format:"%H" -2 "$file_path")
array=()

# Parse the commit sha's.
while read -r sha; do
    array+=("$sha")
done <<<"$shas"

# Now launch the difftool to see the file difference.
echo git difftool --no-prompt ${array[1]}...${array[0]} "${file_path}"
git difftool --no-prompt ${array[1]}...${array[0]} "${file_path}"