Add mkdir -p behaviour for output file to simplify harnesses

src/cli/output.rs

@@ -1,4 +1,4 @@
-use std::fs::File;
+use std::fs::{create_dir_all, File};
 use std::path::Path;
 use rand::Rng;
 use crate::cli::cli::OutputFormat;
@@ -13,6 +13,14 @@ pub fn write<R: Rng, P: Position, S: Storage<P>, W: Walker<P>, Sp: Spawner<P>, S
     format: OutputFormat,
     output: &Path,
 ) {
+    // If the parent does not exist (and we are not in the root or operating a relative 1-component-length path))
+    // create it. This greatly simplifies the harness code.
+    if let Some(parent) = output.parent() &&
+        parent.to_str().map(|x| x != "").unwrap_or(true) &&
+        !parent.exists() {
+        create_dir_all(parent).expect("Failed to create path to output");
+    }
+
     match format {
         OutputFormat::FullDataJson => write_json_full_data(sys, output),
         OutputFormat::Positions => write_csv_positions(sys, output),