Add link to git-cop

Author: unixorn

README.md

@@ -225,6 +225,7 @@ Here are some helpful aliases for your `~/.gitconfig`
 * [git-branches](https://github.com/shurcooL/git-branches) - Prints the commit behind/ahead counts for branches.
 * [git-bump](https://github.com/arrdem/git-bump) - Hook scripts to automatically bump the version file in a repository
 * [git-chart](https://github.com/flashcode/gitchart) - A python script that builds charts from a git repository
+* [git-cop](https://github.com/bkuhlmann/git-cop) - Enforces Git rebase workflow with consistent Git commits for a clean and easy to read/debug project history.
 * [git-crypt](https://www.agwa.name/projects/git-crypt/) - Enables transparent encryption and decryption of files in a git repository. Files which you choose to protect are encrypted when committed, and decrypted when checked out.
 * [git-deploy-s3](https://github.com/bradt/git-deploy-s3) - Keeps your git repo's assets in sync with Amazon S3.
 * [git-diffall](https://github.com/thenigan/git-diffall) - Provides a directory based diff mechanism for git.