Git Repository Splitting

Splitting mono-repo into  a logical repos by applying filters

1. git clone --bare https://github.com/egovernments/old-repository.git

2. cd old-repository.git
3. Remove all the unwanted branches     
   1. git branch -D <branchname> <branchname> <branchname> ...
4. Pick the folder you want separated out from entire repo
   git filter-branch --subdirectory-filter rainmaker/ -- master
5. Optionally remove few modules from previously applied filter, say if rainmaker folder has 7 modules out of which you need only 

   git filter-branch -f --prune-empty --index-filter 'git rm --cached --ignore-unmatch egov-search-indexer/ *egov-mdms-service-depreciated/* ' master

6. Check if repo structure is as needed, check current remote
   git remote -v

7. Push to new repo git push --mirror https://github.com/digit-egov/new-repository.git

Sparse Checkout

1. Pick the folder you want separated out from entire repo
      mkdir myrepo & cd myrepo & git init

   
   

2. Applied filters, add the folders that you need to separate 

git config core.sparseCheckout true

git remote add -f origin git://digit-egov/NEW-REPOSITORY-NAME.git

echo "path/within_repo/to/desired_subdir/*" > .git/info/sparse-checkout

git checkout [branchname] # ex: master

1. Push to new repo
   git push -u origin master

To duplicate a repository without forking it, you can run a special clone command, then mirror-push to the new repository.

1. Create a new directory as per choice

2. Create a bare clone of the repository.

   $ git clone --bare https://github.com/egovernments/old-repository.git

3. Mirror-push to the new repository. (_{you must create the new repository on GitHub. In these examples, digit-egov/new-repository or digit-egov/mirrored are the mirrors.})

   $ cd old-repository.git
   $ git push --mirror https://github.com/digit-egov/new-repository.git

4. Remove the temporary local repository you created in step 1.

   $ cd ..
   $ rm -rf old-repository.git

Mirroring a repository that contains Git Large File Storage objects

1. Open Terminal.

2. Create a bare clone of the repository. Replace the example username with the name of the person or organization who owns the repository, and replace the example repository name with the name of the repository you'd like to duplicate.

   $ git clone --bare https://github.com/egovernments/old-repository.git

3. Navigate to the repository you just cloned.

   $ cd old-repository.git

4. Pull in the repository's Git Large File Storage objects.

   $ git lfs fetch --all

5. Mirror-push to the new repository.

   $ git push --mirror https://github.com/digit-egov/new-repository.git

6. Push the repository's Git Large File Storage objects to your mirror.

   $ git lfs push --all https://github.com/digit-egov/new-repository.git

7. Remove the temporary local repository you created in step 1.

   $ cd ..
   $ rm -rf old-repository.git

Mirroring a repository in another location

If you want to mirror a repository in another location, including getting updates from the original, you can clone a mirror and periodically push the changes.

1. Open Terminal.

2. Create a bare mirrored clone of the repository.

   $ git clone --mirror https://github.com/egovernments/repository-to-mirror.git

3. Set the push location to your mirror.

   $ cd repository-to-mirror.git
   $ git remote set-url --push origin https://github.com/digit-egov/mirrored

As with a bare clone, a mirrored clone includes all remote branches and tags, but all local references will be overwritten each time you fetch, so it will always be the same as the original repository. Setting the URL for pushes simplifies pushing to your mirror. To update your mirror, fetch updates and push.

$ git fetch -p origin
$ git push --mirror

Related articles

https://help.github.com/en/articles/splitting-a-subfolder-out-into-a-new-repository

https://git-scm.com/docs/git-filter-branch

https://help.github.com/en/articles/duplicating-a-repository

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  Git Repository Splitting