fmt: show error if goal > default width

src/uu/fmt/src/fmt.rs

@@ -101,6 +101,9 @@ impl FmtOptions {
                 (w, g)
             }
             (None, Some(&g)) => {
+                if g > DEFAULT_WIDTH {
+                    return Err(USimpleError::new(1, "GOAL cannot be greater than WIDTH."));
+                }
                 let w = (g * 100 / DEFAULT_GOAL_TO_WIDTH_RATIO).max(g + 3);
                 (w, g)
             }

tests/by-util/test_fmt.rs

@@ -93,6 +93,17 @@ fn test_fmt_goal_too_big() {
     }
 }
 
+#[test]
+fn test_fmt_goal_bigger_than_default_width_of_75() {
+    for param in ["-g", "--goal"] {
+        new_ucmd!()
+            .args(&["one-word-per-line.txt", param, "76"])
+            .fails()
+            .code_is(1)
+            .stderr_is("fmt: GOAL cannot be greater than WIDTH.\n");
+    }
+}
+
 #[test]
 fn test_fmt_invalid_goal() {
     for param in ["-g", "--goal"] {