Use variables directly inside format strings

Most systems should have an up to date Rust compiler by now, so we should be
fine.

src/command.rs

@@ -90,12 +90,12 @@ pub enum SeekDirection {
 impl fmt::Display for SeekDirection {
     fn fmt(&self, f: &mut fmt::Formatter<'_>) -> fmt::Result {
         let repr = match self {
-            SeekDirection::Absolute(pos) => format!("{}", pos),
+            SeekDirection::Absolute(pos) => format!("{pos}"),
             SeekDirection::Relative(delta) => {
                 format!("{}{}", if delta > &0 { "+" } else { "" }, delta)
             }
         };
-        write!(f, "{}", repr)
+        write!(f, "{repr}")
     }
 }
 
@@ -113,7 +113,7 @@ impl fmt::Display for InsertSource {
             InsertSource::Clipboard => "".into(),
             InsertSource::Input(url) => url.to_string(),
         };
-        write!(f, "{}", repr)
+        write!(f, "{repr}")
     }
 }
 
@@ -315,12 +315,12 @@ impl fmt::Display for CommandParseError {
     fn fmt(&self, f: &mut fmt::Formatter<'_>) -> fmt::Result {
         use CommandParseError::*;
         let formatted = match self {
-            NoSuchCommand { cmd } => format!("No such command \"{}\"", cmd),
+            NoSuchCommand { cmd } => format!("No such command \"{cmd}\""),
             InsufficientArgs { cmd, hint } => {
                 if let Some(hint_str) = hint {
-                    format!("\"{}\" requires additional arguments: {}", cmd, hint_str)
+                    format!("\"{cmd}\" requires additional arguments: {hint_str}")
                 } else {
-                    format!("\"{}\" requires additional arguments", cmd)
+                    format!("\"{cmd}\" requires additional arguments")
                 }
             }
             BadEnumArg { arg, accept } => {
@@ -330,9 +330,9 @@ impl fmt::Display for CommandParseError {
                     accept.join("|")
                 )
             }
-            ArgParseError { arg, err } => format!("Error with argument \"{}\": {}", arg, err),
+            ArgParseError { arg, err } => format!("Error with argument \"{arg}\": {err}"),
         };
-        write!(f, "{}", formatted)
+        write!(f, "{formatted}")
     }
 }