gru: A JavaScript repository from cjfont

What is gru?

Gru (Git Repo Unifier) is a tool that offers a flexible solution to having a project's codebase distributed across multiple git repositories. It allows you to clone one repo and have the contents of another repo automatically merged in, but excluded from the first repo's index of tracked files. This in turn allows a project's entire codebase to be pulled in from different repos and set up for development while constricting git to only see files/directories from one repo at a time. Gru can be used as a drop-in replacement for all git commands, since all parameters passed to gru are proxied through to git itself — it does all its work by adding side effects to some of the common git commands. This behavior is controlled in the gru.yml config file, which gru will look for and parse in each repo it handles.

The relationship between repos is established by saying that the derived repo inherits content from one or more base repos; this concept of inheritance is borrowed from object-oriented programming. By including a gru.yml config file at the root of the repo, you can define one or more repos whose files you want essentially treated as part of the project on your local copy. Within the config file, gru expects the property derives-from to be an array of the sources the repo will inherit from.

The command gru clone <repo> will first run the usual git clone command to do the respective clone, then it will look for the gru.yml file and recursively clone any repo it lists under derives-from, after which it will copy its file structure to the derived repo. Each file that is copied to the derived repo is also added to git's .git/info/exclude file which behaves exactly like .gitignore but whose rules are only applicable to the local repo.

Why not simply use submodules?

Git's submodules allow a project to reference other git repositories as sources to be included in the current repository, and similarly can recursively clone all dependent submodules into the project.

Submodules are the appropriate tool to use when the other repository you're referencing is a library or another dependency that can be embedded as a subdirectory, but not when it contains the main project root that you want your current repository to extend from. Gru permits the final arrangement of files and directories for the combined repos to be completely independent from the origin of the files.

What are some practical use cases for gru?

Cases where you want two portions of the same project to remain completely separate from each other, but allow them to overlap the same directory hierarchy (i.e. separating additional private files that may be scattered throughout a public directory tree).
Applying complex access control to projects down to the file level, where file permissions are determined by those of the repo that contains them.
Aggregating scattered repositories of config or data files to facilitate editing and testing.

Installation

Make sure you have NPM installed, then run:

npm install -g gru

Usage

To clone a repo that contains a gru.yml file:

gru clone <repo>

Example gru.yml file:

derives-from:
  - https://github.com/user/first-base-repo
  - https://github.com/user/another-base-repo

More commands/options to follow...

Note that this project is still in the early stages of development and should not be used to blindly deploy code to production.

TODO