Fix some clippy lints

Some might actually improve perf

src/bin/bat/app.rs

@@ -80,6 +80,7 @@ impl App {
         let paging_mode = match self.matches.value_of("paging") {
             Some("always") => PagingMode::Always,
             Some("never") => PagingMode::Never,
+            // FIXME: `_` will always cover in or patterns
             Some("auto") | _ => {
                 if self.matches.occurrences_of("plain") > 1 {
                     // If we have -pp as an option when in auto mode, the pager should be disabled.
@@ -147,6 +148,7 @@ impl App {
                 match self.matches.value_of("wrap") {
                     Some("character") => WrappingMode::Character,
                     Some("never") => WrappingMode::NoWrapping,
+                    // FIXME: `_` will always cover in or patterns
                     Some("auto") | _ => {
                         if style_components.plain() {
                             WrappingMode::NoWrapping
@@ -249,18 +251,18 @@ impl App {
 
         let mut filenames_or_none: Box<dyn Iterator<Item = _>> = match filenames {
             Some(ref filenames) => {
-                Box::new(filenames.into_iter().map(|name| Some(OsStr::new(*name))))
+                Box::new(filenames.iter().map(|name| Some(OsStr::new(*name))))
             }
             None => Box::new(std::iter::repeat(None)),
         };
         let files: Option<Vec<&OsStr>> = self.matches.values_of_os("FILE").map(|vs| vs.collect());
 
         if files.is_none() {
-            let input = Input::stdin().with_name(filenames_or_none.nth(0).unwrap_or(None));
+            let input = Input::stdin().with_name(filenames_or_none.next().unwrap_or(None));
             return Ok(vec![input]);
         }
         let files_or_none: Box<dyn Iterator<Item = _>> = match files {
-            Some(ref files) => Box::new(files.into_iter().map(|name| Some(*name))),
+            Some(ref files) => Box::new(files.iter().map(|name| Some(*name))),
             None => Box::new(std::iter::repeat(None)),
         };
 
@@ -274,7 +276,7 @@ impl App {
                 }
             }
         }
-        return Ok(file_input);
+        Ok(file_input)
     }
 
     fn style_components(&self) -> Result<StyleComponents> {

src/bin/bat/assets.rs

@@ -53,5 +53,5 @@ pub fn assets_from_cache_or_binary() -> Result<HighlightingAssets> {
         }
     }
 
-    Ok(HighlightingAssets::from_cache(&cache_dir).unwrap_or(HighlightingAssets::from_binary()))
+    Ok(HighlightingAssets::from_cache(&cache_dir).unwrap_or_else(|_| HighlightingAssets::from_binary()))
 }

src/bin/bat/clap_app.rs

@@ -180,7 +180,7 @@ pub fn build_app(interactive_output: bool) -> ClapApp<'static, 'static> {
                         t.parse::<i32>()
                             .map_err(|_e| "must be an offset or number")
                             .and_then(|v| if v == 0 && !is_offset {
-                                Err("terminal width cannot be zero".into())
+                                Err("terminal width cannot be zero")
                             } else {
                                 Ok(())
                             })

src/bin/bat/config.rs

@@ -35,10 +35,10 @@ pub fn generate_config_file() -> bat::error::Result<()> {
         match config_dir {
             Some(path) => fs::create_dir_all(path)?,
             None => {
-                return Ok(Err(format!(
+                return Err(format!(
                     "Unable to write config file to: {}",
                     config_file.to_string_lossy()
-                ))?)
+                ).into());
             }
         }
     }
@@ -77,7 +77,7 @@ pub fn generate_config_file() -> bat::error::Result<()> {
         config_file.to_string_lossy()
     );
 
-    return Ok(());
+    Ok(())
 }
 
 pub fn get_args_from_config_file() -> Result<Vec<OsString>, shell_words::ParseError> {

src/bin/bat/main.rs

@@ -70,7 +70,7 @@ pub fn list_languages(config: &Config) -> Result<()> {
 
     if config.loop_through {
         for lang in languages {
-            write!(stdout, "{}:{}\n", lang.name, lang.file_extensions.join(","))?;
+            writeln!(stdout, "{}:{}", lang.name, lang.file_extensions.join(","))?;
         }
     } else {
         let longest = languages