Consistently append newlines regardless of colour mode

CHANGELOG.md

@@ -1,5 +1,10 @@
 ## 0.43 (unreleased)
 
+### Display
+
+Fixed an issue with single-column display when colour is disabled,
+where newlines were missing from the output.
+
 ### Command Line Interface
 
 `--help` now shows the default value for all arguments (it was

src/display/side_by_side.rs

@@ -340,11 +340,11 @@ pub fn print(
         (
             split_on_newlines(lhs_src)
                 .iter()
-                .map(|s| (*s).to_owned())
+                .map(|s| format!("{}\n", s))
                 .collect(),
             split_on_newlines(rhs_src)
                 .iter()
-                .map(|s| (*s).to_owned())
+                .map(|s| format!("{}\n", s))
                 .collect(),
         )
     };

src/display/style.rs

@@ -289,7 +289,8 @@ fn group_by_line(
     ranges_by_line
 }
 
-/// Apply the `Style`s to the spans specified.
+/// Apply the `Style`s to the spans specified. Return a vec of the
+/// styled strings, including trailing newlines.
 ///
 /// Tolerant against lines in `s` being shorter than the spans.
 fn style_lines(lines: &[&str], styles: &[(SingleLineSpan, Style)]) -> Vec<String> {