lohr/README.org

#+title: lohr

=lohr= is a Git mirroring tool.

I created it to solve a simple problem I had: I host my own git server at
[[https://git.alarsyo.net]], but want to mirror my public projects to GitHub /
GitLab, for backup and visibility purposes.

GitLab has a mirroring setting, but it doesn't allow for multiple mirrors, as
far as I know. I also wanted my instance to be the single source of truth.

** How it works

Gitea is setup to send webhooks to my =lohr= server on every push update. When
=lohr= receives a push, it clones the concerned repository, or updates it if
already cloned. Then it pushes the update to *all remotes listed* in the [[file:.lohr][.lohr]]
file at the repo root.

*** Destructive

This is a very destructive process: anything removed from the single source of
truth is effectively removed from any mirror as well.

** Installing

=lohr= is [[https://crates.io/crates/lohr][published on crates.io]], so you can install it with ~cargo install~:

#+begin_src sh
$ cargo install lohr
#+end_src

** Setup

*** Quickstart

Setting up =lohr= should be quite simple:

1. Create a =Rocket.toml= file and [[https://rocket.rs/v0.4/guide/configuration/][add your configuration]].

2. Export a secret variable:

   #+begin_src sh
   $ export LOHR_SECRET=42 # please don't use this secret
   #+end_src

3. Run =lohr=:

   #+begin_src sh
   $ cargo run # or `cargo run --release` for production usage
   #+end_src

4. Configure your favorite git server to send a webhook to =lohr='s address on
   every push event.

   I used [[https://docs.gitea.io/en-us/webhooks/][Gitea's webhooks format]], but I *think* they're similar to GitHub and
   GitLab's webhooks, so these should work too! (If they don't, *please* file an
   issue!)

   Don't forget to set the webhook secret to the one you chose above.

5. Add a =.lohr= file containing the remotes you want to mirror this repo to:

   #+begin_example
   git@github.com:you/your_repo
   #+end_example

   and push it. That's it! =lohr= is mirroring your repo now.

*** Configuration

**** Home directory

=lohr= needs a place to clone repos and store its data. By default, it's the
current directory, but you can set the =LOHR_HOME= environment variable to
customize it.

**** Shared secret

As shown in the quickstart guide, you *must* set the =LOHR_SECRET= environment
variable.

**** Extra remote configuration

You can provide =lohr= with a YAML file containing additional configuration. You
can pass its path to the =--config= flag when launching =lohr=. If no
configuration is provided via a CLI flag, =lohr= will check the =LOHR_CONFIG=
environment variable. If the environment variable isn't set either, it will
check in =LOHR_HOME= is a =lohr-config.yaml= file exists, and try to load it.

This file takes the following format:

#+begin_src yaml
default_remotes:
  - "git@github:user"
  - "git@gitlab:user"

additional_remotes:
  - "git@git.sr.ht:~user"

blacklist:
  - "private-.*"
#+end_src

- ~default_remotes~ is a list of remotes to use if no ~.lohr~ file is found in a
  repository.
- ~additional_remotes~ is a list of remotes to add in any case, whether the
  original set of remotes is set via ~default_remotes~ or via a =.lohr= file.
- ~blacklist~ is a list of regular expressions to match against the full
  repository names. Any that matches will not be mirrored, even if it contains a
  `.lohr` file.

Both settings take as input a list of "stems", i.e. incomplete remote addresses,
to which the repo's name will be appended (so for example, if my
~default_remotes~ contains ~git@github.com:alarsyo~, and a push event webhook
is received for repository =git@gitlab.com:some/long/path/repo_name=, then the
mirror destination will be =git@github.com:alarsyo/repo_name=.

** Contributing

I accept patches anywhere! Feel free to [[https://github.com/alarsyo/lohr/pulls][open a GitHub Pull Request]], [[https://gitlab.com/alarsyo/lohr/-/merge_requests][a GitLab
Merge Request]], or [[https://lists.sr.ht/~alarsyo/lohr-dev][send me a patch by email]]!

** Why lohr?

I was looking for a cool name, and thought about the Magic Mirror in Snow White.
Some *[[https://en.wikipedia.org/wiki/Magic_Mirror_(Snow_White)][furious wikipedia searching]]* later, I found that the Magic Mirror was
probably inspired by [[http://spessartmuseum.de/seiten/schneewittchen_engl.html][the Talking Mirror in Lohr am Main]]. That's it, that's the
story.

** License

=lohr= is distributed under the terms of both the MIT license and the Apache
License (Version 2.0).

See [[file:LICENSE-APACHE][LICENSE-APACHE]] and [[file:LICENSE-MIT][LICENSE-MIT]] for details.