breaking: reserve a data directory for the application

multibinary/src/main.rs

@@ -1,4 +1,20 @@
+use std::path::PathBuf;
+
+use clap::Parser;
+
+#[derive(Debug, Parser)]
+struct Args {
+    #[arg(
+        long,
+        env,
+        default_value_os_t = dirs_next::data_local_dir().expect("sorry but you're on a platform where dirs_next::data_local_dir() returned None, so please specify a data directory for the application").join("ac-qu-ai-nt")
+    )]
+    application_data_directory: PathBuf,
+}
+
 fn main() {
+    let args = Args::parse();
+
     #[cfg(feature = "cli-clap")]
     ac_qu_ai_nt_cli_clap::main();
 }