Fix tip commit helper function

src/lib.rs

@@ -396,13 +396,7 @@ impl BenchmarkRepository
 	fn tip_commit<'repository>(repository: &'repository git2::Repository, branch_name: &str) -> Result<git2::Commit<'repository>, git2::Error>
 	{
 		let tip_reference_name = format!("refs/remotes/origin/{}", branch_name);
-		let tip_reference = match repository.find_reference(&tip_reference_name)
-		{
-			Ok(value) => value,
-			Err(error) => panic!("Could not find reference “{}”: {}", tip_reference_name, error),
-		};
-
-		tip_reference.peel_to_commit()
+		repository.find_reference(&tip_reference_name).and_then(|tip_reference| tip_reference.peel_to_commit())
 	}
 
 	pub fn join(&self)