uucore/num_format: the default precision for %g is 6

src/uucore/src/lib/features/format/num_format.rs

@@ -286,7 +286,13 @@ impl Formatter for Float {
 
         let precision = match precision {
             Some(CanAsterisk::Fixed(x)) => x,
-            None => 0,
+            None => {
+                if matches!(variant, FloatVariant::Shortest) {
+                    6
+                } else {
+                    0
+                }
+            }
             Some(CanAsterisk::Asterisk) => return Err(FormatError::WrongSpecType),
         };