sort: add comments to wait_if_signal function and its usage

src/uu/sort/src/sort.rs

@@ -1268,6 +1268,8 @@ pub fn uumain(args: impl uucore::Args) -> UResult<()> {
     settings.init_precomputed();
 
     let result = exec(&mut files, &settings, output, &mut tmp_dir);
+    // Wait here if `SIGINT` was received,
+    // for signal handler to do its work and terminate the program.
     tmp_dir.wait_if_signal();
     result
 }

src/uu/sort/src/tmp_dir.rs

@@ -45,7 +45,8 @@ impl TmpDirWrapper {
         let path = self.temp_dir.as_ref().unwrap().path().to_owned();
         let lock = self.lock.clone();
         ctrlc::set_handler(move || {
-            // Take the lock so that `next_file_path` returns no new file path.
+            // Take the lock so that `next_file_path` returns no new file path,
+            // and the program doesn't terminate before the handler has finished
             let _lock = lock.lock().unwrap();
             if let Err(e) = remove_tmp_dir(&path) {
                 show_error!("failed to delete temporary directory: {}", e);
@@ -70,6 +71,7 @@ impl TmpDirWrapper {
         ))
     }
 
+    /// Function just waits if signal handler was called
     pub fn wait_if_signal(&self) {
         let _lock = self.lock.lock().unwrap();
     }