init: This is the initial commit.

This commit marks the start of the project. This adds a simple
command line interface which can be found in `src/cli.rs`.

src/cli.rs

@@ -0,0 +1,114 @@
+use std::path::PathBuf;
+
+use yansi::Paint;
+
+pub fn print_help() {
+    println!(
+        "{} {} - the bucky language compiler",
+        "buckyc".bold(),
+        env!("CARGO_PKG_VERSION").dim()
+    );
+
+    println!();
+    println!("{}", "USAGE:".bold().yellow());
+    println!("  fluxc [OPTIONS] <file> [<file> ...]");
+
+    println!();
+    println!("{}", "OPTIONS:".bold().yellow());
+    println!(
+        "  {}, {}    Print this help message",
+        "-h".bold(),
+        "--help".bold()
+    );
+    println!(
+        "  {}, {}  Print version information",
+        "-V".bold(),
+        "--version".bold()
+    );
+    println!(
+        "  {}              Emit IR and stop (implies `-c`)",
+        "-S".bold()
+    );
+    println!(
+        "  {}              Compile to object file (no linking)",
+        "-c".bold()
+    );
+    println!(
+        "  {} {}      Write output to <file>",
+        "-o".bold(),
+        "<file>".bold(),
+    );
+
+    println!();
+    println!("{}", "ARGS:".bold().yellow());
+    println!(
+        "  {}    One or more Flux source files to compile",
+        "<file>".bold(),
+    );
+}
+
+pub fn print_version() {
+    println!("buckyc {}", env!("CARGO_PKG_VERSION"));
+}
+
+pub fn fatal(message: impl ToString) -> ! {
+    eprintln!("{}: {}", "error".bold().red(), message.to_string().bold());
+    std::process::exit(1);
+}
+
+#[derive(Debug)]
+pub struct Opts {
+    /// The list of files passed to the compiler.
+    pub files: Vec<PathBuf>,
+    /// `-S`: emit IR and stop (implies `-c`).
+    pub emit_ir: bool,
+    /// `-c`: compile source to object file without linking.
+    pub no_link: bool,
+    /// `-o <file>`: write final output to this path.
+    pub output: Option<PathBuf>,
+}
+
+pub fn parse_args() -> Opts {
+    let mut files = Vec::new();
+    let mut no_link = false;
+    let mut emit_ir = false;
+    let mut output = None;
+
+    let mut args = std::env::args().skip(1).peekable();
+    while let Some(arg) = args.next() {
+        match arg.as_str() {
+            "-h" | "--help" => {
+                print_help();
+                std::process::exit(0);
+            }
+            "-V" | "--version" => {
+                print_version();
+                std::process::exit(0);
+            }
+            "-c" => no_link = true,
+            "-S" => {
+                emit_ir = true;
+                no_link = true
+            }
+            "-o" => match args.next() {
+                Some(path) => output = Some(path.into()),
+                None => fatal("option `-o` requires an argument"),
+            },
+            flag if flag.starts_with('-') => {
+                fatal(format!("unknown option `{flag}`"));
+            }
+            path => files.push(path.into()),
+        }
+    }
+
+    if files.is_empty() {
+        fatal("no input files - at least one source file is required");
+    }
+
+    Opts {
+        files,
+        emit_ir,
+        no_link,
+        output,
+    }
+}