show buggy behavior of not trimming newlines in new credential process test

tests/testsuite/credential_process.rs

@@ -695,3 +695,22 @@ fn alias_builtin_warning() {
         )
         .run();
 }
+
+#[cargo_test]
+fn login_token_from_stdin() {
+    // Test reading a token from stdin, ensuring newlines are trimmed.
+    let registry = registry::RegistryBuilder::new()
+        .no_configure_token()
+        .credential_provider(&[&build_provider("test-cred", r#"{"Ok": {"kind": "login"}}"#)])
+        .build();
+
+    cargo_process("login")
+        .replace_crates_io(registry.index_url())
+        .with_stdin("abcdefg\n")
+        .with_stderr(
+            r#"[UPDATING] [..]
+{"v":1,"registry":{"index-url":"https://github.com/rust-lang/crates.io-index","name":"crates-io"},"kind":"login","token":"abcdefg\n","login-url":"[..]"}
+"#,
+        )
+        .run();
+}