refactor: extract --jobserver-auth= to a free function

Author: weihanglo

src/lib.rs

@@ -279,11 +279,7 @@ impl Client {
             }
         };
 
-        let (arg, pos) = match ["--jobserver-fds=", "--jobserver-auth="]
-            .iter()
-            .map(|&arg| var.find(arg).map(|pos| (arg, pos)))
-            .find_map(|pos| pos)
-        {
+        let (arg, pos) = match find_jobserver_auth(var) {
             Some((arg, pos)) => (arg, pos),
             None => return FromEnv::new_err(FromEnvErrorInner::NoJobserver, env, var_os),
         };
@@ -588,6 +584,13 @@ impl HelperState {
     }
 }
 
+fn find_jobserver_auth(var: &str) -> Option<(&str, usize)> {
+    ["--jobserver-fds=", "--jobserver-auth="]
+        .iter()
+        .map(|&arg| var.find(arg).map(|pos| (arg, pos)))
+        .find_map(|pos| pos)
+}
+
 #[test]
 fn no_helper_deadlock() {
     let x = crate::Client::new(32).unwrap();