Add sample file pair that has shown a ton of hunk merging bugs

sample_files/bad_combine_new.rs

@@ -0,0 +1,19 @@
+fn display_line_nums(
+) -> (String, String) {
+    let display_rhs_line_num: String = match rhs_line_num {
+        Some(line_num) => {
+            let s = format_line_num_padded(line_num, widths.rhs_line_nums);
+            if rhs_lines_with_novel.contains(&line_num) {
+                s.bright_green().to_string()
+            } else {
+                s
+            }
+        }
+        None => format_missing_line_num(
+            prev_rhs_line_num.unwrap_or_else(|| 10.into()),
+            widths.rhs_line_nums,
+        ),
+    };
+
+    (display_lhs_line_num, display_rhs_line_num)
+}

sample_files/bad_combine_old.rs

@@ -0,0 +1,29 @@
+
+fn column_widths(
+    hunks: &[Hunk],
+    lhs_mps: &[MatchedPos],
+    rhs_mps: &[MatchedPos],
+    max_lhs_src_line: LineNumber,
+    max_rhs_src_line: LineNumber,
+)  {
+}
+
+fn display_line_nums(
+) -> (String, String) {
+    let display_rhs_line_num: String = match rhs_line_num {
+        Some(line_num) => {
+            let s = format_line_num_padded(line_num, rhs_column_width);
+            if rhs_lines_with_novel.contains(&line_num) {
+                s.bright_green().to_string()
+            } else {
+                s
+            }
+        }
+        None => format_missing_line_num(
+            prev_rhs_line_num.unwrap_or_else(|| 10.into()),
+            rhs_column_width,
+        ),
+    };
+
+    (display_lhs_line_num, display_rhs_line_num)
+}