quick code migration from one repository to another

migrate_git

#!/usr/bin/env bash

#
# Requirements:
#
#   1. git >= 2.25
#   2. git-filter-repo
#   3. bash >= 4.0
#
# Installation:
#
#   1. Make a copy of this file
#   2. $ chmod +x migrate_git
#
# Usage:
#
#   1. Modify SOURCE, TARGET and DIRS_TO_MOVE according to your needs.
#   2. ./migrate_git
#   3. Chill
#


set -e

SOURCE="git@github.com:owner/repo.git"
TARGET="git@github.com:owner/repo.git"
declare -A DIRS_TO_MOVE
DIRS_TO_MOVE=(
  ["source/path/to/dir"]="target/path/to/dir"
)

source_remote="origin"
source_branch="master"
target_remote="target"
target_branch="master"
work_branch="__repo_migration"

################################################################################

echo "
Welcome to repository migration! Moving to new home is a very stressful
activity. I am here to help you make it easier and seamless!

Please note that I will not push to any of the repositories, as it's your
responsibility.

Roughly, here are steps I am going to perform:

1. Clone source repository.
2. Remove all commits not related to the files that must be moved.
3. Add target repository as additional remote and fetch it.
4. Rebase on top of target repository.

--------------------------------------------------------------------------------
"

echo "Moving
"
for s in "${!DIRS_TO_MOVE[@]}"; do
  echo "  - $s -> ${DIRS_TO_MOVE[$s]}"
done
echo "
  from: $SOURCE
  to:   $TARGET
"

################################################################################

function check() {
  command -v "$1" >/dev/null 2>&1
}

check git-filter-repo || {
  echo "--------------------------------------------------------------------------------"
  echo
  echo "{•̃_•̃} Awww snap!"
  echo
  echo "git-filter-repo is required for this script to work!"
  echo
  echo "More info: https://github.com/newren/git-filter-repo"
  echo "  $ brew install git-filter-repo"
  echo "  # pacman -S git-filter-repo"
  echo
  exit 1
}

#

################################################################################

repo="repository"
if [ ! -d "$repo/.git" ]; then
  rm -rf "$repo"
  git clone "$SOURCE" "$repo"
fi

cd "$repo" && {
  echo "fetch the latest changes from $SOURCE"
  git fetch "$source_remote"

  if [ "$(git rev-parse --abbrev-ref HEAD)" != "$work_branch" ]; then
    git checkout -b "$work_branch" "$source_remote/$source_branch"
  fi
  git reset --hard "$source_remote/$source_branch"

  args=""
  for p in "${!DIRS_TO_MOVE[@]}"; do
    args="--path $p/ $args"
  done
  # shellcheck disable=SC2086
  git filter-repo --force $args

  # rename rules
  for s in "${!DIRS_TO_MOVE[@]}"; do
    git filter-repo --path-rename "$s":"${DIRS_TO_MOVE[$s]}"
  done

  if ! git config "remote.$target_remote.url" > /dev/null; then
    git remote add "$target_remote" "$TARGET"
  fi

  echo "fetch the latest changes from $TARGET"
  git fetch "$target_remote"
  git rebase "$target_remote/$target_branch"

  echo "fix committer name and email"
  export FILTER_BRANCH_SQUELCH_WARNING=1
  git filter-branch --commit-filter 'export GIT_COMMITTER_NAME="$GIT_AUTHOR_NAME"; export GIT_COMMITTER_EMAIL="$GIT_AUTHOR_EMAIL"; export GIT_COMMITTER_DATE="$GIT_AUTHOR_DATE"; git commit-tree "$@"' -- "$target_remote/$target_branch"..HEAD
}

echo "(⊃｡•́‿•̀｡)⊃"
echo "     \\_done!"
echo
echo "        verify repository at $repo"
echo "        and push it using"
echo "        $ git push $target_remote $work_branch"