Don't allow ouch to compress the root folder

src/compressors/zip.rs

@@ -1,7 +1,4 @@
-use std::{
-    io::{Cursor, Write},
-    path::PathBuf,
-};
+use std::{io::{Cursor, Write}, path::PathBuf};
 
 use walkdir::WalkDir;
 
@@ -57,7 +54,11 @@ impl ZipCompressor {
         for filename in input_filenames {
 
             let previous_location = utils::change_dir_and_return_parent(&filename)?;
-            let filename = filename.file_name()?;
+            let filename = filename
+                .file_name()
+                // Safe unwrap since the function call above would fail in scenarios 
+                // where this unwrap would panic
+                .unwrap();
 
             for entry in WalkDir::new(filename) {
                 let entry = entry?;

src/error.rs

@@ -73,4 +73,4 @@ impl From<walkdir::Error> for Error {
         eprintln!("{}: {}", "error".red(), err);
         Self::InvalidInput
     }
-}
+}

src/utils.rs

@@ -63,7 +63,17 @@ pub(crate) fn get_destination_path(dest: &Option<File>) -> &Path {
 
 pub (crate) fn change_dir_and_return_parent(filename: &PathBuf) -> crate::Result<PathBuf> {
     let previous_location = env::current_dir()?;
-    let parent = filename.parent().unwrap();
+    
+    let parent = if let Some(parent) = filename.parent() {
+        parent
+    } else {
+        let spacing = "          ";
+        println!("{} It seems you're trying to compress the root folder.", "[WARNING]".red());
+        println!("{}This is unadvisable since ouch does compressions in-memory.", spacing);
+        println!("{}Use a more appropriate tool for this, such as {}.", spacing, "rsync".green());
+        return Err(crate::Error::InvalidInput);
+    };
+
     env::set_current_dir(parent)?;
     Ok(previous_location)
 }