code-extractor

Extracts code from from one repository to another preserving history

How it works

The code extractor works by cloning a source repository into a specified destination and running git filter-branch to extract the specified files and directories. Once it has completed, the new repository will be left with a master branch with the extracted code with preserved history which can be pushed into a new upstream repository. Additionally, there will be a "deletion branch" named extract_$name, which can be used to push a deletion commit to the source repository.

Installation

Just install the gem via rubygems:

$ gem install code-extractor

Or if you want to do it yourself, the lib/code_extractor.rb file is a standalone ruby script, so you can just download that and run it with a modern ruby version.

Usage

Configuration

Create a file named extractions.yml with the configuration. For example:

---
:name: extracted_thing
:upstream: git@github.com:SourceOrg/source_repo.git
:upstream_branch: master
:upstream_name: SourceOrg/source_repo
:extractions:
  - file1
  - dir1/file2
  - dir2
:destination: /dev/new_repo

• :name - The name of the feature being extracted. This will be used as part of the "deletion branch" name as well as the commit message to that branch.
• :upstream - The git repository URL from which the extraction will occur.
• :upstream_branch - The branch on :upstream from which the extraction will occur. Defaults to "master" if not set.
• :upstream_name - The name of the repository from with the extraction will occur. This will be used in the extracted commit messages to relate back to the original repository. With the example yaml above, this would cause the following to be added to the commit messages: (transferred from SourceOrg/source_repo@$GIT_COMMIT)
• :extractions - An array of files and directories to be extracted.
• :destination - The target directory for the extracted repository.

Execution

If you have install this as a gem, you can just run:

$ code-extractor

But if you installed this manually, just either make the script executable, or run it with the ruby interpreter via.

$ ruby code_extractor.rb

This shouldn't be run in the directory of the original repository, but instead in an empty directory where the clone can be created and modified.

Post-execution

• Push the master branch to a new target repository. For example:

  git remote add upstream git@github.com:SomeOrg/new_repo.git
  git push -u upstream master
  

• Create a pull request to delete the extracted code from the source repository. For example:

  git remote add source git@github.com:SomeOrg/source_repo.git
  git push -u source extract_$name
  # Create a pull request from the extract_$name branch