Add --number option for showing line numbers. Also adds related options:

    - format string for specifying minus number line
    - format string for specifying plus number line
    - minus number style
    - plus number style
    - minus format string style
    - plus format string style

src/cli.rs

@@ -127,6 +127,24 @@ within a style string):
    Specifying colors like this is useful if your terminal only supports 256 colors (i.e. doesn\'t
    support 24-bit color).
 
+LINE NUMBERS
+------------
+
+Options that have a name like --*-format allow you to specify a string to display for the line
+number columns. The string should specify the location of the line number using the placeholder
+%ln.
+
+For example, to display the line numbers divided by specific characters:
+
+    8 ⋮   9 │ Here is an output line
+    9 ⋮  10 │ Here is another output line
+   10 ⋮  11 │ Here is the line number
+
+you would use the following input:
+
+--number-minus-format '%ln ⋮'
+--number-plus-format '%ln │'
+
 If something isn't working correctly, or you have a feature request, please open an issue at
 https://github.com/dandavison/delta/issues.
 "
@@ -245,6 +263,52 @@ pub struct Opt {
     /// given.
     pub hunk_header_decoration_style: String,
 
+    /// Display line numbers next to the diff. The first column contains line
+    /// numbers in the previous version of the file, and the second column contains
+    /// line number in the new version of the file. A blank cell in the first or
+    /// second column indicates that the line does not exist in that file (it was
+    /// added or removed, respectively).
+    #[structopt(short = "n", long = "number")]
+    pub show_line_numbers: bool,
+
+    /// Style (foreground, background, attributes) for the left (minus) column of line numbers
+    /// (--number), if --number is set. See STYLES section.
+    /// Defaults to --hunk-style.
+    #[structopt(long = "number-minus-style", default_value = "auto")]
+    pub number_minus_style: String,
+
+    /// Style (foreground, background, attributes) for the right (plus) column of line numbers
+    /// (--number), if --number is set. See STYLES section.
+    /// Defaults to --hunk-style.
+    #[structopt(long = "number-plus-style", default_value = "auto")]
+    pub number_plus_style: String,
+
+    /// Format string for the left (minus) column of line numbers (--number), if --number is set.
+    /// Should include the placeholder %ln to indicate the position of the line number.
+    /// See the LINE NUMBERS section.
+    /// Defaults to '%ln⋮'
+    #[structopt(long = "number-minus-format", default_value = "%ln⋮")]
+    pub number_minus_format: String,
+
+    /// Format string for the right (plus) column of line numbers (--number), if --number is set.
+    /// Should include the placeholder %ln to indicate the position of the line number.
+    /// See the LINE NUMBERS section.
+    /// Defaults to '%ln│ '
+    #[structopt(long = "number-plus-format", default_value = "%ln│ ")]
+    pub number_plus_format: String,
+
+    /// Style (foreground, background, attributes) for the left (minus) line number format string
+    /// (--number), if --number is set. See STYLES section.
+    /// Defaults to --hunk-style.
+    #[structopt(long = "number-minus-format-style", default_value = "auto")]
+    pub number_minus_format_style: String,
+
+    /// Style (foreground, background, attributes) for the right (plus) line number format string
+    /// (--number), if --number is set. See STYLES section.
+    /// Defaults to --hunk-style.
+    #[structopt(long = "number-plus-format-style", default_value = "auto")]
+    pub number_plus_format_style: String,
+
     #[structopt(long = "color-only")]
     /// Do not alter the input in any way other than applying colors. Equivalent to
     /// `--keep-plus-minus-markers --width variable --tabs 0 --commit-decoration ''

src/config.rs

@@ -41,12 +41,19 @@ pub struct Config<'a> {
     pub navigate: bool,
     pub null_style: Style,
     pub null_syntect_style: SyntectStyle,
+    pub number_minus_format: String,
+    pub number_minus_format_style: Style,
+    pub number_minus_style: Style,
+    pub number_plus_format: String,
+    pub number_plus_format_style: Style,
+    pub number_plus_style: Style,
     pub paging_mode: PagingMode,
     pub plus_emph_style: Style,
     pub plus_file: Option<PathBuf>,
     pub plus_line_marker: &'a str,
     pub plus_non_emph_style: Style,
     pub plus_style: Style,
+    pub show_line_numbers: bool,
     pub syntax_dummy_theme: SyntaxTheme,
     pub syntax_set: SyntaxSet,
     pub syntax_theme: Option<SyntaxTheme>,
@@ -120,6 +127,13 @@ pub fn get_config<'a>(
     let (commit_style, file_style, hunk_header_style) =
         make_commit_file_hunk_header_styles(&opt, true_color);
 
+    let (
+        number_minus_format_style,
+        number_minus_style,
+        number_plus_format_style,
+        number_plus_style,
+    ) = make_line_number_styles(&opt, hunk_header_style.decoration_ansi_term_style(), true_color);
+
     let syntax_theme = if syntax_theme::is_no_syntax_highlighting_theme_name(&syntax_theme_name) {
         None
     } else {
@@ -164,12 +178,19 @@ pub fn get_config<'a>(
         navigate: opt.navigate,
         null_style: Style::new(),
         null_syntect_style: SyntectStyle::default(),
+        number_minus_format: opt.number_minus_format,
+        number_minus_format_style: number_minus_format_style,
+        number_minus_style: number_minus_style,
+        number_plus_format: opt.number_plus_format,
+        number_plus_format_style: number_plus_format_style,
+        number_plus_style: number_plus_style,
         paging_mode,
         plus_emph_style,
         plus_file: opt.plus_file.map(|s| s.clone()),
         plus_line_marker,
         plus_non_emph_style,
         plus_style,
+        show_line_numbers: opt.show_line_numbers,
         syntax_dummy_theme,
         syntax_set,
         syntax_theme,
@@ -264,6 +285,60 @@ fn make_hunk_styles<'a>(
     )
 }
 
+fn make_line_number_styles<'a>(
+    opt: &'a cli::Opt,
+    default_style: Option<ansi_term::Style>,
+    true_color: bool,
+) -> (Style, Style, Style, Style) {
+    let (default_foreground, default_background) = match default_style {
+        Some(default_style) => (default_style.foreground, default_style.background),
+        None => (None, None)
+    };
+
+    let number_minus_format_style = Style::from_str(
+        &opt.number_minus_format_style,
+        default_foreground,
+        default_background,
+        None,
+        true_color,
+        false,
+    );
+
+    let number_minus_style = Style::from_str(
+        &opt.number_minus_style,
+        default_foreground,
+        default_background,
+        None,
+        true_color,
+        false,
+    );
+
+    let number_plus_format_style = Style::from_str(
+        &opt.number_plus_format_style,
+        default_foreground,
+        default_background,
+        None,
+        true_color,
+        false,
+    );
+
+    let number_plus_style = Style::from_str(
+        &opt.number_plus_style,
+        default_foreground,
+        default_background,
+        None,
+        true_color,
+        false,
+    );
+
+    (
+        number_minus_format_style,
+        number_minus_style,
+        number_plus_format_style,
+        number_plus_style,
+    )
+}
+
 fn make_commit_file_hunk_header_styles(opt: &cli::Opt, true_color: bool) -> (Style, Style, Style) {
     (
         Style::from_str_with_handling_of_special_decoration_attributes_and_respecting_deprecated_foreground_color_arg(

src/delta.rs

@@ -369,7 +369,9 @@ fn handle_hunk_header_line(
             draw::write_no_decoration
         }
     };
-    let (raw_code_fragment, line_number) = parse::parse_hunk_metadata(&line);
+    let (raw_code_fragment, line_numbers) = parse::parse_hunk_metadata(&line);
+    painter.minus_line_number = line_numbers[0];
+    painter.plus_line_number = line_numbers[line_numbers.len() - 1];
     if config.hunk_header_style.is_raw {
         writeln!(painter.writer)?;
         draw_fn(
@@ -397,6 +399,7 @@ fn handle_hunk_header_line(
             Painter::paint_lines(
                 syntax_style_sections,
                 vec![vec![(config.hunk_header_style, &lines[0])]],
+                vec![None],
                 &mut painter.output_buffer,
                 config,
                 "",
@@ -418,10 +421,14 @@ fn handle_hunk_header_line(
             };
         }
     };
-    match config.hunk_header_style.decoration_ansi_term_style() {
-        Some(style) => writeln!(painter.writer, "{}", style.paint(line_number))?,
-        None => writeln!(painter.writer, "{}", line_number)?,
-    };
+
+    if !config.show_line_numbers {
+        let line_number = &format!("{}", painter.plus_line_number);
+        match config.hunk_header_style.decoration_ansi_term_style() {
+            Some(style) => writeln!(painter.writer, "{}", style.paint(line_number))?,
+            None => writeln!(painter.writer, "{}", line_number)?,
+        }
+    }
     Ok(())
 }
 
@@ -474,13 +481,19 @@ fn handle_hunk_line(
             Painter::paint_lines(
                 syntax_style_sections,
                 vec![diff_style_sections],
+                vec![Some((
+                    Some(painter.minus_line_number),
+                    Some(painter.plus_line_number),
+                ))],
                 &mut painter.output_buffer,
                 config,
                 prefix,
                 config.zero_style,
                 config.zero_style,
                 None,
             );
+            painter.minus_line_number += 1;
+            painter.plus_line_number += 1;
             state
         }
         _ => {