Merge pull request #5 from cspr-rad/add-readme

add README.md

README.md

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+# Kairos
+
+## Development
+
+To get started developing on this repository you can leverage Nix. The following sections explain how to obtain a development shell and how to build the project.
+
+### Development Shell
+
+You have two options here, you can configure and leverage [direnv](https://direnv.net/) to automatically drop you in a development shell (recommended) or do it manually.
+
+#### Automatic Development Shell using `direnv`
+
+First, you will have to install direnv, by adding it to your Nix/NixOS configuration or using your package manager.
+Afterward, run:
+
+```sh
+touch .envrc
+echo "use flake" >> .envrc
+direnv allow
+```
+
+#### Manual Development Shell
+
+Run:
+
+```sh
+nix develop
+```
+
+#### Risc0 Development Shell
+
+Because `risc0` projects require a fork of `rustc`, we decided to detach the development shell for `kairos-prover` from the other crates. To enter a development shell when working with the `kairos-prover`/`risc0` projects, run:
+
+If you don't use `direnv`, you will first need to enter the default development shell, if you didn't before:
+
+```sh
+nix develop 
+```
+
+Afterward (the only command you need when you use `direnv`):
+
+```
+nix develop .#risczero
+```
+
+### Inside a Development Shell
+
+Inside the development shell, you can use `cargo` as usual during development.
+
+### Formatting
+
+Code for the whole project tree can be formatted by running `nix fmt` from the project's root or anywhere in the tree, but be warned that it will only format code inside the sub-tree.
+
+The `nix fmt` command currently formats all the `Rust` and `Nix` code in the tree. To add support for more languages you'll have to adjust the `treefmt` attribute-set in the `flake.nix` accordingly. A list of already supported formatters can be found [here](https://numtide.github.io/treefmt/formatters/). Note that any formatting tool can be added trivially, if stuck contact your Nix expert.
+
+### Build
+
+You can explore the buildable outputs of this project easily by running:
+
+```sh
+nix flake show
+```
+
+To build e.g. `kairos` you can then run:
+
+```sh
+nix build .#kairos
+```
+
+### Check
+
+To run all the "checks" of this project, like formatting, lint, audit, etc. checks, run:
+
+```sh
+nix flake check
+```
+
+To run a single check e.g. the format check, run:
+
+```sh
+nix build .#checks.<system>.treefmt
+```