How to extract a subproject
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|How to extract a subproject|
Sometimes, a piece of functionality is developed as part of one project, but grows so much as to warrant becoming its own, separate project.
This tutorial describes how to split part of a Git repository into its own dedicated Git repository, preserving only the history relevant to the subproject being extracted.
Extract the revision history
- Use Git's filter-branch feature to extract the Git history of only the subproject:
git filter-branch -f --prune-empty --subdirectory-filter <subdir>Where
<subdir>is the folder containing the subproject's source code.
Update the Maven build
Assuming you are using Maven to build the subproject:
- Add an <scm> section to the pom.xml to reflect the new remote repository's URL (see example):
vi pom.xml git commit -m 'Add SCM location' pom.xml
- Replace the old <parent> with a new one, such as pom-scijava, pom-imagej or pom-fiji (see example)—or remove the <parent> altogether.
- Add a <developers> section to the pom.xml to indicate the project developers (see example). You can also add <contributors> if desired and relevant.
- Make sure the project still builds:
mvn clean package
- Add (or adjust) the .gitignore file (see example).
Push the changes
- Make sure that all your changes look good:
git status git diffThis is good advice in general: check
git diffevery time before you commit, to prevent making a fool out of yourself.
- Commit everything, mentioning the commit of the parent project from which history was rewritten (see example):
git add . && git commit -s
- Create a new repository somewhere for the new project—we recommend GitHub.
- Connect your repository with the remote one:
git remote set-url origin firstname.lastname@example.org:my-org/my-new-projectWhere email@example.com:my-org/my-new-project is the remote URL for the new project's dedicated repository.
- Push the resultant history to the project's new repository:
git push -u origin master
Change any online resources
- Edit the relevant web page(s) to reflect the new Git repository location
- Update any other known links to the project