Add CLI interface for exporting to `cuboid` model

models/cuboid/src/main.rs

@@ -1,8 +1,10 @@
-use std::ops::Deref;
+use std::{ops::Deref, path::PathBuf};
 
 use fj_kernel::algorithms::{approx::Tolerance, triangulate::Triangulate};
 
 fn main() -> anyhow::Result<()> {
+    let args = Args::parse();
+
     let cuboid = cuboid::cuboid(3., 2., 1.);
 
     // The tolerance makes no difference for this model, as there aren't any
@@ -10,7 +12,30 @@ fn main() -> anyhow::Result<()> {
     let tolerance = Tolerance::from_scalar(1.)?;
 
     let mesh = (cuboid.deref(), tolerance).triangulate();
+
+    if let Some(path) = args.export {
+        fj_export::export(&mesh, &path)?;
+    } else {
         fj_window::run(mesh, false)?;
+    }
 
     Ok(())
 }
+
+/// Standardized CLI for Fornjot models
+#[derive(clap::Parser)]
+pub struct Args {
+    /// Export model to this path
+    #[arg(short, long, value_name = "PATH")]
+    pub export: Option<PathBuf>,
+}
+
+impl Args {
+    /// Parse the command-line arguments
+    ///
+    /// Convenience method that saves the caller from having to import the
+    /// `clap::Parser` trait.
+    pub fn parse() -> Self {
+        <Self as clap::Parser>::parse()
+    }
+}