fix: Let the line number width start at 1

	fix rust-lang#57

Author: chengr4

src/renderer/display_list.rs

@@ -79,7 +79,7 @@ impl<'a> Display for DisplayList<'a> {
             })
         });
         let lineno_width = if lineno_width == 0 {
-            lineno_width
+            lineno_width + 1
         } else if self.anonymized_line_numbers {
             ANONYMIZED_LINE_NUM.len()
         } else {

tests/formatter.rs

@@ -193,7 +193,7 @@ fn test_format_footer_title() {
         .footer(Level::Error.title("This __is__ a title"));
     let expected = str![[r#"
 error
- = error: This __is__ a title
+  = error: This __is__ a title
 "#]];
     let renderer = Renderer::plain();
     assert_data_eq!(renderer.render(input).to_string(), expected);
@@ -279,9 +279,9 @@ fn test_only_source() {
         .snippet(Snippet::source("").origin("file.rs"));
     let expected = str![[r#"
 error
---> file.rs
- |
- |
+ --> file.rs
+  |
+  |
 "#]];
     let renderer = Renderer::plain();
     assert_data_eq!(renderer.render(input).to_string(), expected);