"rebase" onto codebase that moved to different directory

rebase-to-moved.sh

#! /bin/bash
# usage: rebase-to-moved.sh my-branch
# will create tag backup of current branch and rebase it on a moved directory

if [ -n "$(git status --porcelain)" ]; then 
    echo "You need to have clean working copy"
    exit 1
fi;

git checkout $1

git merge-base --is-ancestor 250d09f7e5ef64f7e8c449e2ea3f5636b0f8ac57 $1 

if [[ $? -ne 0 ]]; then
    echo "Please run 'git rebase -i 250d09f7e5ef64f7e8c449e2ea3f5636b0f8ac57' first"
    exit 1
fi 

git merge-base --is-ancestor 8195138a5cab7a00715503fb86cb4c769e48be91 $1

if [[ $? -eq 0 ]]; then
    echo "Everything is already OK"
    exit 1
fi 

set -e

CD=$( dirname "${BASH_SOURCE[0]}" )

rm -rf $CD/patches

git format-patch -M -C --output-directory "$CD/patches" 8195138a5cab7a00715503fb86cb4c769e48be91..$1 

ls -d $CD/patches/* | xargs -n1 -I {} sh -c "sed -i -r 's@diff --git a/([^ ]*) b/([^ ]*)@diff --git a/legacy-app/\1 b/legacy-app/\2@' {}"
ls -d $CD/patches/* | xargs -n1 -I {} sh -c "sed -i -r 's@--- a/([^ ]*)@--- a/legacy-app/\1@' {}"
ls -d $CD/patches/* | xargs -n1 -I {} sh -c "sed -i -r 's@\+\+\+ b/([^ ]*)@+++ b/legacy-app/\1@' {}"
ls -d $CD/patches/* | xargs -n1 -I {} sh -c "sed -i -r 's@([^ ]*) mode ([^ ]*) ([^ ]*)@\1 mode \2 legacy-app/\3@' {}"
ls -d $CD/patches/* | xargs -n1 -I {} sh -c "sed -i -r 's@rename (from|to)? ?([^ ]*)@rename \1 legacy-app/\2@' {}"

git tag $1-backup $1 || true
git checkout $1
git reset --hard 8195138a5cab7a00715503fb86cb4c769e48be91
git am $CD/patches/*

Ref.: https://gist.github.com/fejjo/425a615170b24a837c6aa7d19eb6af73