Add --conclude option with tests

This implementation of --conclude is basically identical
to the existing implementation for --prepare. I have not
adapted any existing tests. All tests which test --conclude
functionality are new.

The --conclude commands will run in the same order in which
they are supplied on the cli in the same manner as --prepare
and there must either be one --conclude command, or else the
same number of --concludes as there are commands.

tests/integration_tests.rs

@@ -75,6 +75,31 @@ fn fails_with_wrong_number_of_prepare_options() {
         ));
 }
 
+#[test]
+fn fails_with_wrong_number_of_conclude_options() {
+    hyperfine()
+        .arg("--runs=1")
+        .arg("--conclude=echo a")
+        .arg("--conclude=echo b")
+        .arg("echo a")
+        .arg("echo b")
+        .assert()
+        .success();
+
+    hyperfine()
+        .arg("--runs=1")
+        .arg("--conclude=echo a")
+        .arg("--conclude=echo b")
+        .arg("echo a")
+        .arg("echo b")
+        .arg("echo c")
+        .assert()
+        .failure()
+        .stderr(predicate::str::contains(
+            "The '--conclude' option has to be provided",
+        ));
+}
+
 #[test]
 fn fails_with_duplicate_parameter_names() {
     hyperfine()
@@ -167,6 +192,18 @@ fn fails_for_unknown_prepare_command() {
         ));
 }
 
+#[test]
+fn fails_for_unknown_conclude_command() {
+    hyperfine()
+        .arg("--conclude=some-nonexisting-program-b5d9574198b7e4b12a71fa4747c0a577")
+        .arg("echo test")
+        .assert()
+        .failure()
+        .stderr(predicate::str::contains(
+            "The conclusion command terminated with a non-zero exit code.",
+        ));
+}
+
 #[cfg(unix)]
 #[test]
 fn can_run_failing_commands_with_ignore_failure_option() {
@@ -320,6 +357,48 @@ fn takes_preparation_command_into_account_for_computing_number_of_runs() {
         .stdout(predicate::str::contains("30 runs"));
 }
 
+#[test]
+fn takes_conclusion_command_into_account_for_computing_number_of_runs() {
+    hyperfine_debug()
+        .arg("--conclude=sleep 0.02")
+        .arg("sleep 0.01")
+        .assert()
+        .success()
+        .stdout(predicate::str::contains("100 runs"));
+
+    // Shell overhead needs to be added to both the conclude command and the actual command,
+    // leading to a total benchmark time of (cmd + shell + conclude + shell = 0.1 s)
+    hyperfine_debug()
+        .arg("--shell=sleep 0.01")
+        .arg("--conclude=sleep 0.03")
+        .arg("sleep 0.05")
+        .assert()
+        .success()
+        .stdout(predicate::str::contains("30 runs"));
+}
+
+#[test]
+fn takes_both_preparation_and_conclusion_command_into_account_for_computing_number_of_runs() {
+    hyperfine_debug()
+        .arg("--prepare=sleep 0.01")
+        .arg("--conclude=sleep 0.01")
+        .arg("sleep 0.01")
+        .assert()
+        .success()
+        .stdout(predicate::str::contains("100 runs"));
+
+    // Shell overhead needs to be added to both the prepare, conclude and the actual command,
+    // leading to a total benchmark time of (prepare + shell + cmd + shell + conclude + shell = 0.1 s)
+    hyperfine_debug()
+        .arg("--shell=sleep 0.01")
+        .arg("--prepare=sleep 0.01")
+        .arg("--conclude=sleep 0.01")
+        .arg("sleep 0.05")
+        .assert()
+        .success()
+        .stdout(predicate::str::contains("30 runs"));
+}
+
 #[test]
 fn shows_benchmark_comparison_with_relative_times() {
     hyperfine_debug()