upload: check that directory is a directory

upload/src/config.rs

···
+use std::fs;
+
 pub struct Config {
   pub user: String,
   pub pword: String,
···
     && let Some(pword) = pword.clone()
     && let Some(dir) = dir.clone()
   {
-    return Ok(Config {
-      user,
-      pword,
-      dir: dir.to_owned(),
-    });
+    if let Ok(metadata) = fs::metadata(dir.clone())
+      && metadata.is_dir()
+    {
+      return Ok(Config {
+        user,
+        pword,
+        dir: dir.to_owned(),
+      });
+    } else {
+      return Err(ConfigErr::NotADirectory);
+    }
   }
 
   return Err(ConfigErr::NotEnoughArgs(String::from(