Cupper
Cupper allows for the update of services that are created using cookiecutter. When run, it creates a new branch that contains the latest cookiecuttered code, using a JSON file with context that matches the existing service. This file can be created through cookiecutter with the following contents:
{{ cookiecutter | jsonify }}
The script takes two arguments: a JSON file containing configuration for cookiecutter, and the name of the branch to create.
cupper .cookiecutter.json template
You can then merge these changes into your existing code:
git merge template
This code is heavily based on https://github.com/aroig/cookiecutter-latex-paper/blob/master/make/cookiecutter-update.py, with a few very small changes.
Note that you will need a recent version of git for this to work (it needs --no-checkout on git worktree)
Use --checkout REV or -c REV to check out a specific template revision. This option is forwarded to cookiecutter, and takes a branch, tag, or commit which should be checked out by cookiecutter after cloning the template repository.