Replace direnv with Rust

[domenkozar]

We're not using many features of direnv, and maintaining the long direnvrc in bash is tedious work.

Most importanty, it doesn't handle background processing of changes, which leads to poor DX.

We'd rebuild the environment in the background and then reload it if it succeeded, notifying the shell/TUI about it and say what changed.

[mrene]

I have a related issue, I'm loading a devenv shell (defined via flake-parts) using direnv, but when running devenv up after making changes, it doesn't seem to reload the processes/tasks even though there is some nix evaluation happening. Most likely, it's inheriting ${DEVENV_TASKS} from the shell, but I would expect the devenv shim to replace it with fresh values if it's already evaluating the shell.

direnv reload resolves this issue

[domenkozar]

This would be specially useful if editors like Zed would support devenv natively.

[amiorin]

I use this workaround: define a task that creates the .envrc and run devenv build at the same time. To generate the environment files, I have created this project: BigConfig but a Makefile will cut it too if you don't need tempating.

https://github.com/purcell/envrc/issues/119