Handle singular case for incompatible rules warning (#13212)

Co-authored-by: Micha Reiser <micha@reiser.io>

crates/ruff/src/commands/format.rs

@@ -810,7 +810,11 @@ pub(super) fn warn_incompatible_formatter_settings(resolver: &Resolver) {
             .map(|rule| format!("`{}`", rule.noqa_code()))
             .collect();
         rule_names.sort();
-        warn_user_once!("The following rules may cause conflicts when used with the formatter: {}. To avoid unexpected behavior, we recommend disabling these rules, either by removing them from the `select` or `extend-select` configuration, or adding them to the `ignore` configuration.", rule_names.join(", "));
+        if let [rule] = rule_names.as_slice() {
+            warn_user_once!("The following rule may cause conflicts when used with the formatter: {rule}. To avoid unexpected behavior, we recommend disabling this rule, either by removing it from the `select` or `extend-select` configuration, or adding it to the `ignore` configuration.");
+        } else {
+            warn_user_once!("The following rules may cause conflicts when used with the formatter: {}. To avoid unexpected behavior, we recommend disabling these rules, either by removing them from the `select` or `extend-select` configuration, or adding them to the `ignore` configuration.", rule_names.join(", "));
+        }
     }
 
     // Next, validate settings-specific incompatibilities.

crates/ruff/tests/format.rs

@@ -785,7 +785,7 @@ if condition:
     	print('Should change quotes')
 
     ----- stderr -----
-    warning: The following rules may cause conflicts when used with the formatter: `COM812`. To avoid unexpected behavior, we recommend disabling these rules, either by removing them from the `select` or `extend-select` configuration, or adding them to the `ignore` configuration.
+    warning: The following rule may cause conflicts when used with the formatter: `COM812`. To avoid unexpected behavior, we recommend disabling this rule, either by removing it from the `select` or `extend-select` configuration, or adding it to the `ignore` configuration.
     "###);
     Ok(())
 }