Simpler install

[sand7000]

This addresses:

#48

It adds a script to simplify installation a bit and it adds a RUSTUP_TOOLCHAIN env var to wrapper.rs to make sure the installed tools always use the right toolchain.

[RyanGlScott]

Thanks for the PR!

I am quite happy with the RUSTUP_TOOLCHAIN changes in wrapper.rs. I have more mixed feelings about the introduction of a wrapper script, since it's yet another way way to install mir-json that we would need to maintain going forward (e.g., remembering to update the toolchain version). That being said, it does replace multiple cargo/rustup commands with a single script, so I can see the appeal behind it. I won't push back if others are on board.

[RyanGlScott]

Instead of putting the exact shell commands to run here, I'd recommend pointing folks to the instructions at https://rustup.rs instead, as it actually recommends running a different command than what is listed here. What's more, this would future-proof the script in the event that the https://rustup.rs instructions change later.

[sand7000]

Ah, I took the command from the README which has a link to an old version of the rust book. I will fix both the script and the readme.

[sand7000]

I have more mixed feelings about the introduction of a wrapper script, since it's yet another way way to install mir-json that we would need to maintain going forward

This is fair although I find maintaining a README to be more error prone and more likely to fall out of date than a testable script. Case in point the Rust book reference in our README was already out of date.

[RyanGlScott]

OK. I generally prefer to know exactly what cargo commands are being run under the hood, and if we ever want to upload mir-json to crates.io someday, then I suspect that we will have to make the installation script as close to a series of one or two cargo commands as possible. That being said, the installation script is small enough that it is easy to audit by hand, so I think I am fine with it.

@spernsteiner @qsctr, do you have any thoughts on this?

[qsctr]

I don't have strong feelings about this. I think the toolchain and component installations can actually be combined into one command, like we document in wrapper.rs:

mir-json/src/bin/wrapper.rs

Line 48 in 92d2e94

" rustup toolchain install {} --force --component rustc-dev,rust-src",

(speaking of which, that line probably should be updated to just ./install-mir-json.sh, if we decide we are using the script.)

At that point, the shell script really is just turning two commands into one command, so I'm not sure that it's necessary. Also, I think there is some value in having the command for setting up the toolchain and the command for building & installing mir-json itself be separate, in case one of them goes wrong. But that mainly comes from past experiences trying to install software with complex installation scripts that fail somewhere in the middle, and not being able to figure out what went wrong, but as you say, this script is simple enough to inspect, so I guess it's fine.