Git submodules

Cheat Sheet: Setting Up and Managing a Shared Submodule Across Branches

Purpose

You need to share specific files (AI_assist/future_comments.txt, AI_assist/prompts.md, README.md) across multiple branches (master, working, and potentially others in the future). Using a Git submodule, these files are maintained in a separate branch (shared-files), and the submodule is added to all relevant branches to ensure synchronization. This method allows edits in one branch to automatically reflect in all other branches that use the submodule.

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Steps to Achieve the Setup Using Submodules

1. Prepare the shared-files Branch

• This branch will contain only the specific files that need to be shared across other branches.

• Switch to the branch (e.g., master):

  git checkout master
  

• Create the shared-files branch:

  git checkout -b shared-files
  

• Remove all unnecessary files from tracking:

  git rm -r --cached .
  

• Add back only the files you need:

  git add AI_assist/future_comments.txt AI_assist/prompts.md README.md
  

• Commit the changes:

  git commit -m "Initial commit of shared files"
  

• Push the shared-files branch to the remote:

  git push -u origin shared-files
  

2. Add the shared-files Submodule to the master Branch

• Switch to the master branch:

  git checkout master
  

• Remove the duplicate files from the master branch (if present):

  git rm AI_assist/future_comments.txt AI_assist/prompts.md README.md
  git commit -m "Remove duplicate files before adding submodule"
  

• Add the shared-files branch as a submodule in the master branch:

  git submodule add -b shared-files https://github.com/your-username/your-repo.git shared-files
  

  Note: Replace https://github.com/your-username/your-repo.git with your repository URL.

• Commit the submodule addition:

  git commit -m "Add shared-files as submodule in master"
  

3. Repeat the Same for the working Branch

• Switch to the working branch:

  git checkout working
  

• Remove the duplicate files from working:

  git rm AI_assist/future_comments.txt AI_assist/prompts.md README.md
  git commit -m "Remove duplicate files before adding submodule"
  

• Add the submodule to the working branch:

  git submodule add -b shared-files https://github.com/your-username/your-repo.git shared-files
  

• If you encounter a “submodule already exists” error, use the --force option to reuse the existing submodule:

  git submodule add -b shared-files --force https://github.com/your-username/your-repo.git shared-files
  

• Commit the submodule addition:

  git commit -m "Add shared-files as submodule in working"
  

4. Sync Changes Across Branches

• After committing changes to the shared-files submodule in any branch, you need to sync those changes in other branches.

• To pull the latest changes in the submodule:

  git submodule update --remote
  

• If any branch is ahead with local commits, push the changes:

  git push origin <branch-name>
  

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Additional Considerations and Tricky Points

1. Handling Duplicate Files:
   • If files already exist in the branch where you’re adding the submodule, you must remove them using git rm before adding the submodule. Otherwise, you risk having duplicate files and conflict issues.

2. Reusing an Existing Submodule (--force flag):

   If you encounter the error:

   fatal: A git directory for 'shared-files' is found locally...
   

   This happens because Git detects that the submodule already exists locally. To reuse the existing directory, add the --force flag:

   git submodule add -b shared-files --force https://github.com/your-username/your-repo.git shared-files
   

3. Pushing Submodule Changes to Remote:

   • After making changes in the submodule, remember to push the changes:

     git push origin shared-files
     

   • You also need to push the changes in the parent branch (e.g., master, working):

     git push origin master
     

4. Removing Untracked Local Files:
   • Even if files are removed from Git tracking (git rm), they will still exist in your working directory. You need to manually delete them from your system if you don’t need them.

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Commands Summary

• Create a branch

  git checkout -b shared-files
  

• Remove files from tracking

  git rm AI_assist/future_comments.txt AI_assist/prompts.md README.md
  

• Add submodule

  git submodule add -b shared-files https://github.com/your-username/your-repo.git shared-files
  

• Force reuse of existing submodule

  git submodule add -b shared-files --force https://github.com/your-username/your-repo.git shared-files
  

• Update submodule

  git submodule update --remote
  

• Push changes

  git push origin master
  git push origin shared-files
  

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-### End Result

• You now have a submodule (shared-files) in master, working, and any future branches that can share the same files across branches.
• Changes made to these files in any branch will be automatically reflected in all other branches when you update the submodule.

Let me know if you need more tweaks or additional details for the cheat sheet!

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