Added a little xtask to create a source package in one go

This is a wrapper around `npm pack` that temporarily edits the relative
paths out of `Cargo.toml` to make the package work outside of the git
repo.

xtask/src/nodepackage.rs

@@ -0,0 +1,60 @@
+use anyhow::Context;
+use xshell::{cmd, pushd, read_file, write_file};
+
+pub fn generate() -> Result<(), Box<dyn std::error::Error>> {
+    let root = super::root_dir().context("error determining root directory")?;
+    let node_dir = root.join("api").join("sixtyfps-node");
+
+    let cargo_toml_path = node_dir.join("native").join("Cargo.toml");
+
+    println!("Removing relative paths from {}", cargo_toml_path.to_string_lossy());
+
+    let toml_source =
+        read_file(cargo_toml_path.clone()).context("Failed to read Node Cargo.toml")?;
+
+    let mut toml: toml_edit::Document = toml_source.parse().context("Error parsing Cargo.toml")?;
+
+    // Remove all `path = ` entries from dependencies
+    for dep_key in ["dependencies", "build-dependencies"].iter() {
+        let dep_table = match toml[dep_key].as_table_mut() {
+            Some(table) => table,
+            _ => continue,
+        };
+        let deps: Vec<_> = dep_table.iter().map(|(name, _)| name.to_string()).collect();
+        deps.iter().for_each(|name| {
+            dep_table[name].as_inline_table_mut().map(|dep_config| dep_config.remove("path"));
+        });
+    }
+
+    let edited_toml = toml.to_string();
+
+    write_file(cargo_toml_path.clone(), edited_toml).context("Error writing Cargo.toml")?;
+
+    println!("Running npm package to create the tarball");
+
+    {
+        let _p = pushd(node_dir.clone())
+            .context(format!("Error changing to node directory {}", node_dir.to_string_lossy()))?;
+
+        cmd!("npm pack").run()?;
+    }
+
+    println!("Reverting Cargo.toml");
+
+    write_file(cargo_toml_path, toml_source).context("Error writing Cargo.toml")?;
+
+    let package_json_source =
+        read_file(node_dir.join("package.json")).context("Error reading package.json")?;
+
+    let package_json: serde_json::Value = serde_json::from_str(&package_json_source)?;
+
+    let file_name = node_dir.join(format!(
+        "{}-{}.tar.gz",
+        package_json["name"].as_str().unwrap(),
+        package_json["version"].as_str().unwrap()
+    ));
+
+    println!("Source package created and located in {}", file_name.to_string_lossy());
+
+    Ok(())
+}