git-nomad

Synchronize work-in-progress git branches in a light weight fashion. Motivation:

• You frequently work on the same repository from multiple machines, like a laptop and a desktop.
• You frequently rewrite history and use short understandable-by-only-you branch names, making pushing regular branches to git remotes cumbersome.
• You want all the efficiency and synchronization benefits of having a git clone available, meaning external syncing tools like Dropbox or network mounts are right out.
• You want this synchronization to work out-of-the-box with popular third party remote hosts like GitHub.

Usage

Install git-nomad to make it available on your $PATH.

Configure it for a specific git clone:

```console

Needs to be run once for each clone on each machine.

Note that this defaults to your username and hostname.

See --help for overriding this explicitly.

rraval@apollo:~/git-nomad$ git nomad init Wrote Config { user: "rraval", host: "apollo", } ```

Now hack away with your usual git workflow:

console rraval@apollo:~/git-nomad$ git checkout -b feature rraval@apollo:~/git-nomad$ touch new_file rraval@apollo:~/git-nomad$ git add . rraval@apollo:~/git-nomad$ git commit -m "new file"

Whenever you like, you can push the state of your local branches with:

```console

Synchronizes with a remote called origin by default.

See --help for overriding this explicitly.

rraval@apollo:~/git-nomad$ git nomad sync Pushing local branches to origin... 2s Fetching branches from origin... 1s

apollo refs/nomad/apollo/feature -> e02800d10b11ae03a93e43b8f7fc17b70dfe7acf refs/nomad/apollo/master -> fe8bf41bbaf201c0506b60677f03a23da2873fdc ```

At some future point, you wish to pick up development on a different machine:

```console

Only needs to be run once per clone on each machine.

rraval@boreas:~/git-nomad$ git nomad init Wrote Config { user: "rraval", host: "boreas", } ```

You can now run sync on this new machine as well:

```console rraval@boreas:~/git-nomad$ git nomad sync Pushing local branches to origin... 1s Fetching branches from origin... 1s

apollo refs/nomad/apollo/feature -> e02800d10b11ae03a93e43b8f7fc17b70dfe7acf refs/nomad/apollo/master -> fe8bf41bbaf201c0506b60677f03a23da2873fdc boreas refs/nomad/boreas/master -> fe8bf41bbaf201c0506b60677f03a23da2873fdc ```

Which prints out refs to use to pick up where you left off:

```console rraval@boreas:~/git-nomad$ git checkout -b feature refs/nomad/apollo/feature

Hack away where you left off on apollo

```

Let's say that the boreas machine is where development is happening now, so you go back to apollo to throw away the now outdated branch:

```console rraval@apollo:~/git-nomad$ git checkout master rraval@apollo:~/git-nomad$ git branch -D feature Deleted branch feature (was e02800d).

rraval@apollo:~/git-nomad$ git nomad sync Pushing local branches to origin... 1s Fetching branches from origin... 1s Pruning branches at origin... 2s Delete refs/nomad/apollo/feature (was e02800d10b11ae03a93e43b8f7fc17b70dfe7acf)... 0s

apollo refs/nomad/apollo/master -> fe8bf41bbaf201c0506b60677f03a23da2873fdc boreas refs/nomad/boreas/feature -> 3187d762ca557bfa741bc07d47e0b7f8c1777400 refs/nomad/boreas/master -> fe8bf41bbaf201c0506b60677f03a23da2873fdc ```

If you'd like to stop using git-nomad and clean up all the refs it has created:

```console

Needs to be run once per clone where git nomad init has been run.

See also the prune --host option.

rraval@apollo:~/git-nomad$ git nomad prune --all Fetching branches from origin... 1s Pruning branches at origin... 2s Delete refs/nomad/apollo/master (was fe8bf41bbaf201c0506b60677f03a23da2873fdc)... 0s Delete refs/nomad/boreas/feature (was 3187d762ca557bfa741bc07d47e0b7f8c1777400)... 0s Delete refs/nomad/boreas/master (was fe8bf41bbaf201c0506b60677f03a23da2873fdc)... 0s ```

How it works

Git is unabashedly a content-addressed filesystem that manipulates blob, tree, and commit objects. Layered on top of this is a half decent version control system, though this claim is contentious at best.

Git branches are implemented on top of a more general scheme called refs, where the local branch master is simply the commit pointed to by refs/heads/master. Git reserves a few hierarchies for its own use:

• refs/heads/* represent local branches.
• refs/tags/* represent tags.
• refs/remotes/* represent remote branches.

git-nomad works directly with refs to implement its own light weight synchronization scheme:

1. Push local refs/heads/* to remote refs/nomad/{user}/{host}/*. This allows multiple users on multiple hosts to all use git-nomad on the same remote without overwriting data.
2. Fetch remote refs/nomad/{user}/* to local refs/nomad/*. This makes all the host refs for a given user available in a local clone.
3. Prune local refs/nomad/* refs where the corresponding branch has been deleted.

Using refs like this has advantages:

• You only pay the storage cost for the content unique to the branch. The bulk of repository history is shared!
• As refs get cleaned up, gits automatic garbage collection should reclaim space.
• Since these refs are under a separate refs/nomad hierarchy, they are not subject to the usual fast-forward only rules.

Installation

There is a prototype Nix package available but it has not been integrated into Nixpkgs yet.