Fixes mut issue

src/app.rs

@@ -22,6 +22,7 @@ pub enum PagingMode {
     Never,
 }
 
+#[derive(Clone)]
 pub struct Config<'a> {
     /// List of files to print
     pub files: Vec<Option<&'a str>>,

src/line_range.rs

@@ -1,5 +1,6 @@
 use errors::*;
 
+#[derive(Clone)]
 pub struct LineRange {
     pub lower: usize,
     pub upper: usize,

src/main.rs

@@ -149,7 +149,7 @@ fn run() -> Result<bool> {
             Ok(true)
         }
         _ => {
-            let mut config = app.config()?;
+            let config = app.config()?;
             let assets = HighlightingAssets::new();
 
             if app.matches.is_present("list-languages") {
@@ -157,7 +157,7 @@ fn run() -> Result<bool> {
 
                 Ok(true)
             } else if app.matches.is_present("list-themes") {
-                list_themes(&assets, &mut config);
+                list_themes(&assets, &mut config.clone());
 
                 Ok(true)
             } else {

src/style.rs

@@ -59,6 +59,7 @@ impl FromStr for OutputComponent {
     }
 }
 
+#[derive(Clone)]
 pub struct OutputComponents(pub HashSet<OutputComponent>);
 
 impl OutputComponents {