Split the rune CLI up so there are individual binaries for each sub-command

[Michael-F-Bryan]

A suggestion @f0rodo mentioned is being able to split rune run out of the rune CLI to simplify the process of installing from source.

One possible way we could implement this is by creating multiple sub-commands, taking inspiration from how Cargo does custom subcommands.

• rune - a top-level binary which takes rune foo some-args and calls the rune-foo program with some-args as its arguments
• rune-run - execute a Rune
• rune-build - compile a Runefile into a Rune
• rune-graph - take a Runefile and turn it into a DOT graph that can be visualised
• ...

We can then use the required-features field in Cargo.toml to make sure a particular subcommand is only installed when running cargo install with the corresponding feature flag.

For example:

# crates/rune-cli/Cargo.toml
[package]
name = "hotg-rune-cli"

[[bin]]
name = "rune"
path = "src/bin/rune.rs"

[[bin]]
name = "rune-run"
path = "src/bin/rune-run.rs"
required-features = ["run"]

[[bin]]
name = "rune-build"
path = "src/bin/rune-build.rs"
required-features = ["build"]

...

[features]
default = ["run", "build", "..."]
# Subcommands
run = []
build = []
# Normal feature flags for altering behaviour
wasmer-runtime = ["wasmer", "run"]
wasm3-runtime = ["wasm3", "run"]

That way you can run cargo install hotg-rune-cli to get rune run and rune build, or you could choose to just get rune build by using cargo install hotg-rune-cli --no-default-features --features build.