Add /.cargo to gitignore

[bombela]

For reference, here is the content of my local .cargo/config.toml. With this, the Rust language server will autocomplete for the given target instead of using the host's platform.

[build]
target = "avr-atmega328p.json"

[stappersg]

$ git log --patch | sed --silent '/^commit 2f0f679c/,/^commit/p'
commit 2f0f679c22212933791f298f39f8c1fb450afabb
Author: Nathan Henrie <nate@n8henrie.com>
Date:   Sat Jun 11 06:18:05 2022 -0600

    Set reasonable defaults for cargo config
    
    This sets `build-std=core` by default and uses the atmega328p as the
    default target. Users will still need to specify alternate targets if
    desired, but it makes the build process much easier for a default case.

diff --git a/.cargo/config.toml b/.cargo/config.toml
new file mode 100644
index 0000000..be8c515
--- /dev/null
+++ b/.cargo/config.toml
@@ -0,0 +1,5 @@
+[unstable]
+build-std = [ "core" ]
+
+[build]
+target = "avr-unknown-gnu-atmega328"

commit 7032d81c5b4bee5ed4a28bc5c4c783a97ba5b7fb

so closing this merge request

[bombela]

This is wrong.

.cargo is local. It should never be committed. That is the reason for existing beyond Cargo.toml.

Default configuration goes into Cargo.toml. Local goes to .cargo.

See documentation:
https://doc.rust-lang.org/cargo/reference/config.html#hierarchical-structure

[bombela]

Documentation says:

With this structure, you can specify configuration per-package, and even possibly check it into version control. You can also specify personal defaults with a configuration file in your home directory.

So fair enough, the documentation says you can possibly check it in.

I personally develop mostly against atttiny13a, attiny24a. And I always check compatibility with atmega328(p) (because it is so ubiquitous). Therefor I do change the target often. And I do not want to commit this by mistake.

Reading the doc further, the env var CARGO_BUILD_TARGET takes precedence over the config file. And finally, the --target parameter to cargo/rustc takes ultimate precedence (https://doc.rust-lang.org/cargo/reference/config.html#buildtarget).

I do have to find out how to override this target to rust-analyzer. For now I have simply modified .cargo/config.toml as needed. Maybe there is a better way.

TL;DR: committing .cargo/config.toml is probably fine.

[stappersg]

Maybe there is a better way.

Reopened the merge request to get more exposure for it .

[bombela]

I use neovim with coc. Looks like I can add a local config file, which will then pass --target to rust-analyzer. It does mean I have to remember to keep the local coc files and cargo/rustc command lines (or env var) in sync. I wouldn't expect this crate to require active development after the cycle accurate joins master. But I would imagine this sets the example for other crates targeting avr.

https://github.com/neoclide/coc.nvim/wiki/Using-the-configuration-file#configuration-file-resolve

Anyways, I feel like I am bike-shedding here. I don't want to waste anyone's time.