In the development of service-oriented applications we often will use the phrase “source of truth” when referring to data and its ownership. The expectation being that there is generally a single source of truth in the system. Take DNS for example, we generally trust that a nameserver somewhere out there is acting as the single source of truth for a single domain, such as brokenco.de. Without this guarantee, much of our experience on the internet would break down. For the software we write, increasingly GitHub has become the source of truth for the source code itself. So much so that systems have been built on top of GitHub which further wed the software ecosystem to a single source of truth, such as Golang’s dependency definition conventions.

I have no fear of the GitHub acquisition by Microsoft, but I do concern myself with increasingly large single points of failure. A single entity owning too much of my interactions or data makes me feel uneasy. A little timer starts in my brain: how long until the good vibes run out, and this ends up screwing me?

With our source code living in Git, switching up the source of truth has never been easier. I set out recently to take back control for the source of truth for my own free and open source work. Using a server I have at my disposal, I deployed Gitea. Based originally on Gogs, I have found Gitea rather pleasant and simple to work with.

Fortunately, somebody else has written a tool: the gitea-github-migrator which made initializing the Gitea instance with my repositories quite simple. Due to some GitHub rate limits and other weird transient network errors, I ended up running the migrator over and over again until everything was synchronized properly to my server.

A quick look at my GitHub profile and you may notice that nothing has been deleted. My objective is to own the source of truth, not to reduce the redundancy for my source code. Unfortunately as of today, Gitea cannot automatically push to another Git remote (issue #3480), but creating a script which can be configured as a post-receive hook is easy enough:

#!/bin/sh

echo
echo "Mirroring changes to GitHub under ${GITEA_REPO_USER_NAME}/${GITEA_REPO_NAME}"
echo
git push --mirror git@github.com:${GITEA_REPO_USER_NAME}/${GITEA_REPO_NAME}.git
echo

To support this script I needed to set up a few of things:

  1. A newly generated SSH public/private key pair for Gitea to use.
  2. The new SSH public key needed to be added to my GitHub account
  3. The above script gitea-github-mirror installed on the server’s filesystem
  4. The repositories I wished to mirror needed to have a post-receive hook configured which executes gitea-github-mirror

Once the desired repositories have been set up, I only needed to change my local repositories to point somewhere else for their origin remote. Not-too-coincidentally, this is where my previous blog post about transparently switching SSH between Tor and the LAN comes in.

I can now treat GitHub like a public backup for these repositories, and maintain control over the source of truth for each repository I own and maintain.

Mirroring other repositories

Gitea has another feature worth mentioning in this same vein, one which I am only now starting to use: (pull-based) repository mirroring. Inevitably I find myself relying on third-party repositories either as Git submodules, or for source-builds of some piece of software. Rather than trust that those repositories will exist in perpetuity in somebody else’s GitHub organization or user account, Gitea mirroring allows me to create an automatically-updated mirror of the upstream repository. I’ve since found myself creating new organizations in Gitea to house different collections of libraries and tools I depend on, all automatically synchronized by Gitea.

Data provenance is an important subject to me and while not everything is as easily decentralized as Git, I believe it’s worth the effort to try to own your data as much as possible. For those things which are easily added into source control, Gitea and a modicum of extra disk space does the job nicely!

(Of course, this blog post was published to GitHub pages, after being mirrored from my Gitea instance.)