Add multiple --prepare support

Signed-off-by: Saurav Sharma <appdroiddeveloper@gmail.com>

src/hyperfine/benchmark.rs

@@ -234,13 +234,17 @@ pub fn run_benchmark(
     );
 
     // Run init command
-    let prepare_cmd = options
-        .preparation_command
-        .as_ref()
-        .map(|preparation_command| match cmd.get_parameter() {
-            Some((param, value)) => Command::new_parametrized(preparation_command, param, value),
-            None => Command::new(preparation_command),
-        });
+    let mut prepare_cmd = None;
+    if let Some(values) = &options.preparation_command {
+        if num >= values.len() {
+            prepare_cmd = Some(new_command_from_get_parameter(
+                cmd,
+                &values[values.len() - 1],
+            ));
+        } else {
+            prepare_cmd = Some(new_command_from_get_parameter(cmd, &values[num]));
+        }
+    };
     let prepare_res = run_preparation_command(&options.shell, &prepare_cmd, options.show_output)?;
 
     // Initial timing run
@@ -404,3 +408,14 @@ pub fn run_benchmark(
         cmd.get_parameter().map(|p| p.1),
     ))
 }
+
+// Get out new Command from a Command and preparation command
+fn new_command_from_get_parameter<'a>(
+    cmd: &Command<'a>,
+    preparation_command: &'a str,
+) -> Command<'a> {
+    match cmd.get_parameter() {
+        Some((param, value)) => Command::new_parametrized(preparation_command, param, value),
+        None => Command::new(preparation_command),
+    }
+}