Fixes #261 - Better Default implementation for Opt

---
Empty commit to trigger checks again
---
Another empty commit to trigger checks

Includes-commit: 0e9d853e05
Includes-commit: 1237b26493
Includes-commit: 6fdaf38b63
Replicated-from: https://github.com/cloudflare/pingora/pull/272

.bleep

@@ -1 +1 @@
-e91e896243a80fdbac73b5663224459a6e8d1db5
+dad4171e22fa0f38c7dc19247c36f4004d1245de

pingora-core/src/server/configuration/mod.rs

@@ -119,7 +119,7 @@ impl Default for ServerConf {
 /// Command-line options
 ///
 /// Call `Opt::from_args()` to build this object from the process's command line arguments.
-#[derive(Parser, Debug)]
+#[derive(Parser, Debug, Default)]
 #[clap(name = "basic", long_about = None)]
 pub struct Opt {
     /// Whether this server should try to upgrade from a running old server
@@ -163,15 +163,6 @@ pub struct Opt {
     pub conf: Option<String>,
 }
 
-/// Create the default instance of Opt based on the current command-line args.
-/// This is equivalent to running `Opt::parse` but does not require the
-/// caller to have included the `clap::Parser`
-impl Default for Opt {
-    fn default() -> Self {
-        Opt::parse()
-    }
-}
-
 impl ServerConf {
     // Does not has to be async until we want runtime reload
     pub fn load_from_yaml<P>(path: P) -> Result<Self>