Git: Detach subdirectory into a separate git repository.

http://stackoverflow.com/questions/359424/detach-subdirectory-into-separate-git-repository/17864475#17864475

1. Prepare the old repo
   

   pushd 
   git subtree split -P  -b 
   popd
   

   Note: must NOT contain leading or trailing characters btoa != ./btoa/
2. Create the new repo
   

   mkdir 
   pushd 
   
   git init
   git pull 

Link the new repo to Github or wherever

git remote add origin 
git push origin -u master

Cleanup, if desired

popd # get out of 
pushd 

git rm -rf 

Note: This leaves all the historical references in the repository.See the Appendix below if you're actually concerned about having committed a password or you need to decreasing the file size of your .git folder.

...

Walkthrough

These are the same steps as above, but following my exact steps for my repository instead of using .
Here's a project I have for implementing JavaScript browser modules in node:

tree ~/Code/node-browser-compat

node-browser-compat
├── ArrayBuffer
├── Audio
├── Blob
├── FormData
├── atob
├── btoa
├── location
└── navigator

I want to split out a single folder, btoa, into a separate git repository

pushd ~/Code/node-browser-compat/
git subtree split -P btoa -b btoa-only
popd

I now have a new branch, btoa-only, that only has commits for btoa and I want to create a new repository.

mkdir ~/Code/btoa/
pushd ~/Code/btoa/
git init
git pull ~/Code/node-browser-compat btoa-only

Next I create a new repo on Github or bitbucket, or whatever and add it is the origin (btw, "origin" is just a convention, not part of the command - you could call it "remote-server" or whatever you like)

git remote add origin git@github.com:node-browser-compat/btoa.git
git push origin -u master

Happy day!
Note: If you created a repo with a README.md, .gitignore and LICENSE, you will need to pull first:

git pull origin -u master
git push origin -u master

Lastly, I'll want to remove the folder from the bigger repo

git rm -rf btoa

also handy for when you type in the wrong origin

git remote set-url origin https://github.com/....