Store jars in user specific directory (#137)

* use user specific directory

* update changelog

.changelog/unreleased/notes/rust/137-jar-dir.md

@@ -0,0 +1 @@
+A unique directory to store model-checker jars.

rs/modelator/Cargo.toml

@@ -17,6 +17,7 @@ authors = [
 
 [dependencies]
 clap = "=3.0.0-beta.5"
+directories = "4.0.1"
 hex = "0.4.3"
 lazy_static = "1.4.0"
 nom = "7.1.0"

rs/modelator/src/jar.rs

@@ -96,7 +96,10 @@ pub(crate) fn download_jars_if_necessary<P: AsRef<Path>>(modelator_dir: P) -> Re
 
     if !missing_jars.is_empty() {
         // download missing jars
-        println!("[modelator] Downloading model-checkers... ");
+        println!(
+            "[modelator] Downloading model-checkers at \"{}\"...",
+            modelator_dir.as_ref().to_string_lossy()
+        );
         for jar in missing_jars {
             jar.download(&modelator_dir)?;
         }

rs/modelator/src/lib.rs

@@ -126,7 +126,10 @@ impl Default for ModelatorRuntime {
     fn default() -> Self {
         Self {
             model_checker_runtime: ModelCheckerRuntime::default(),
-            dir: env::current_dir().unwrap().join(".modelator"), //Path::new(".modelator").to_path_buf(),
+            dir: directories::ProjectDirs::from("systems", "Informal", "modelator")
+                .expect("there is no valid home directory")
+                .data_dir()
+                .into(), // env::home_dir().unwrap().join(".modelator"), //Path::new(".modelator").to_path_buf(),
         }
     }
 }