return an error if there are more name options than commands

src/hyperfine/error.rs

@@ -49,6 +49,7 @@ impl Error for ParameterScanError {}
 pub enum OptionsError {
     RunsBelowTwo,
     EmptyRunsRange,
+    TooManyCommandNames(usize),
 }
 
 impl fmt::Display for OptionsError {
@@ -56,6 +57,9 @@ impl fmt::Display for OptionsError {
         match *self {
             OptionsError::EmptyRunsRange => write!(f, "Empty runs range"),
             OptionsError::RunsBelowTwo => write!(f, "Number of runs below two"),
+            OptionsError::TooManyCommandNames(n) => {
+                write!(f, "Too many --command-name options: expected {} at most", n)
+            }
         }
     }
 }

src/main.rs

@@ -130,6 +130,12 @@ fn build_hyperfine_options(matches: &ArgMatches<'_>) -> Result<HyperfineOptions,
     options.names = matches
         .values_of("command-name")
         .map(|values| values.map(String::from).collect::<Vec<String>>());
+    if let Some(ref names) = options.names {
+        let command_strings = matches.values_of("command").unwrap();
+        if names.len() > command_strings.len() {
+            return Err(OptionsError::TooManyCommandNames(command_strings.len()));
+        }
+    }
 
     options.preparation_command = matches
         .values_of("prepare")