diffview.sh

#!/bin/bash

readarray -t commits <<< $(git log --reverse --pretty=format:'%h')
readarray -t messages <<< $(git log --reverse --pretty=format:'%s')

if [[ -z "$1" || "$1" == "list" ]]; then
	for i in "${!commits[@]}"; do
		echo -e "${commits[$i]}  $i  ${messages[$i]}"
	done
	exit 0
fi

left=$(git ls-tree -d --name-only ${commits[0]} | sort | head -n1)
right=$(git ls-tree -d --name-only ${commits[0]} | sort | tail -n1)

commit=$1
[[ $commit == ${commits[0]} || $commit == "0" ]] && echo "First commit, nothing to diff" && exit 1

# Instead of commit, accepts also the position of the commit in the history of changes
if [[ ${#commit} -lt 8 ]];
then
	commit=${commits[$commit]}
fi

tempdir=$(mktemp -d)
git worktree add --no-checkout --detach $tempdir
cd $tempdir
git diff --name-only "${commit}~..${commit}" | xargs git checkout "${commit}~" --
mkdir -p $tempdir/{$left,$right}
meld $tempdir/{$left,$right}
cd $OLDPWD
git worktree remove --force $tempdir