Add line-numbers option

README.md

@@ -215,6 +215,7 @@ FLAGS:
                                      The default behavior is to output a space character in place of these markers.
         --light                      Use default colors appropriate for a light terminal background. For more control,
                                      see the other color options.
+        --line-numbers               Show line numbers for each line of the diff hunk.
         --list-languages             List supported languages and associated file extensions.
         --list-theme-names           List available syntax-highlighting color themes.
         --list-themes                List available syntax highlighting themes, each with an example of highlighted diff

src/cli.rs

@@ -187,6 +187,13 @@ pub struct Opt {
     /// or PAGER (BAT_PAGER has priority).
     #[structopt(long = "paging", default_value = "auto")]
     pub paging_mode: String,
+
+    /// Show line numbers for the input and output diffs. The first column shows the line number
+    /// for the original file, and the second column shows line number for the output file.
+    /// A blank cell indicates that the line does not exist in one of the files (was removed
+    /// or added, respectively).
+    #[structopt(long = "line-numbers")]
+    pub show_line_numbers: bool,
 }
 
 #[derive(Clone, Copy, Debug, PartialEq)]

src/config.rs

@@ -36,6 +36,7 @@ pub struct Config<'a> {
     pub no_style: Style,
     pub max_buffered_lines: usize,
     pub paging_mode: PagingMode,
+    pub show_line_numbers: bool,
 }
 
 pub fn get_config<'a>(
@@ -162,6 +163,7 @@ pub fn get_config<'a>(
         no_style: style::get_no_style(),
         max_buffered_lines: 32,
         paging_mode,
+        show_line_numbers: opt.show_line_numbers,
     }
 }
 

src/delta.rs

@@ -246,7 +246,10 @@ fn handle_hunk_meta_line(
         cli::SectionStyle::Plain => panic!(),
         cli::SectionStyle::Omit => return Ok(()),
     };
-    let (raw_code_fragment, line_number) = parse::parse_hunk_metadata(&line);
+    let (raw_code_fragment, line_number_in, line_number_out) = parse::parse_hunk_metadata(&line);
+    painter.line_number_in = line_number_in.parse::<usize>().unwrap_or(0);
+    painter.line_number_out = line_number_out.parse::<usize>().unwrap_or(0);
+
     let code_fragment = prepare(raw_code_fragment, false, config);
     if !code_fragment.is_empty() {
         let syntax_style_sections = Painter::get_line_syntax_style_sections(
@@ -261,6 +264,7 @@ fn handle_hunk_meta_line(
                 style::NO_BACKGROUND_COLOR_STYLE_MODIFIER,
                 &code_fragment,
             )]],
+            vec![prepare_line_numbers(None, None, config)],
             &mut painter.output_buffer,
             config,
             "",
@@ -278,11 +282,19 @@ fn handle_hunk_meta_line(
         )?;
         painter.output_buffer.clear();
     }
-    writeln!(
-        painter.writer,
-        "\n{}",
-        paint::paint_text_foreground(line_number, config.hunk_color, config.true_color)
-    )?;
+    if config.show_line_numbers {
+        writeln!(
+            painter.writer,
+            "",
+        )?;
+    }
+    else {
+        writeln!(
+            painter.writer,
+            "\n{}",
+            paint::paint_text_foreground(line_number_out, config.hunk_color, config.true_color)
+        )?;
+    }
     Ok(())
 }
 
@@ -307,22 +319,28 @@ fn handle_hunk_line(
     {
         painter.paint_buffered_lines();
     }
+    let mut line_numbers = Vec::new();
     match line.chars().next() {
         Some('-') => {
             if state == State::HunkPlus {
                 painter.paint_buffered_lines();
             }
             painter.minus_lines.push(prepare(&line, true, config));
+            line_numbers.push(prepare_line_numbers(Some(painter.line_number_in), None, config));
             State::HunkMinus
         }
         Some('+') => {
             painter.plus_lines.push(prepare(&line, true, config));
+            line_numbers.push(prepare_line_numbers(None, Some(painter.line_number_out), config));
             State::HunkPlus
         }
         Some(' ') => {
             let prefix = if line.is_empty() { "" } else { &line[..1] };
             painter.paint_buffered_lines();
             let line = prepare(&line, true, config);
+            line_numbers.push(prepare_line_numbers(Some(painter.line_number_in), Some(painter.line_number_out), config));
+            painter.line_number_in += 1;
+            painter.line_number_out += 1;
             let syntax_style_sections = Painter::get_line_syntax_style_sections(
                 &line,
                 &mut painter.highlighter,
@@ -332,6 +350,7 @@ fn handle_hunk_line(
             Painter::paint_lines(
                 vec![syntax_style_sections],
                 vec![vec![(style::NO_BACKGROUND_COLOR_STYLE_MODIFIER, &line)]],
+                line_numbers,
                 &mut painter.output_buffer,
                 config,
                 prefix,
@@ -375,6 +394,24 @@ fn prepare(line: &str, append_newline: bool, config: &Config) -> String {
     }
 }
 
+fn _line_number_style(line_number: Option<usize>) -> String {
+    match line_number {
+        Some(x) => format!("{:^4}", x),
+        None => format!("    "),
+    }
+}
+
+pub fn prepare_line_numbers(line_number_in: Option<usize>, line_number_out: Option<usize>, config: &Config) -> String {
+    let formatted = format!(
+        "{}⋮{}",
+        _line_number_style(line_number_in),
+        _line_number_style(line_number_out),
+    );
+    let numbers = paint::paint_text_foreground(&formatted, config.hunk_color, config.true_color);
+    let divider = paint::paint_text_foreground("│", config.hunk_color, config.true_color);
+    format!("{}{}", numbers, divider)
+}
+
 /// Expand tabs as spaces.
 /// tab_width = 0 is documented to mean do not replace tabs.
 fn expand_tabs<'a, I>(line: I, tab_width: usize) -> String
@@ -662,6 +699,7 @@ mod tests {
             list_theme_names: false,
             list_themes: false,
             max_line_distance: 0.3,
+            show_line_numbers: false,
         }
     }
 

src/paint.rs

@@ -9,6 +9,7 @@ use syntect::parsing::{SyntaxReference, SyntaxSet};
 use crate::bat::assets::HighlightingAssets;
 use crate::bat::terminal::to_ansi_color;
 use crate::config;
+use crate::delta::prepare_line_numbers;
 use crate::edits;
 use crate::paint::superimpose_style_sections::superimpose_style_sections;
 use crate::style;
@@ -24,6 +25,8 @@ pub struct Painter<'a> {
     pub highlighter: HighlightLines<'a>,
     pub config: &'a config::Config<'a>,
     pub output_buffer: String,
+    pub line_number_in: usize,
+    pub line_number_out: usize,
 }
 
 impl<'a> Painter<'a> {
@@ -43,6 +46,8 @@ impl<'a> Painter<'a> {
             highlighter: dummy_highlighter,
             writer,
             config,
+            line_number_in: 0,
+            line_number_out: 0,
         }
     }
 
@@ -72,11 +77,23 @@ impl<'a> Painter<'a> {
             );
         let (minus_line_diff_style_sections, plus_line_diff_style_sections) =
             Self::get_diff_style_sections(&self.minus_lines, &self.plus_lines, self.config);
+
+        let mut minus_line_numbers = Vec::new();
+        let mut plus_line_numbers = Vec::new();
+        for _line in &self.minus_lines {
+            minus_line_numbers.push(prepare_line_numbers(Some(self.line_number_in), None, self.config));
+            self.line_number_in += 1;
+        }
+        for _line in &self.plus_lines {
+            plus_line_numbers.push(prepare_line_numbers(None, Some(self.line_number_out), self.config));
+            self.line_number_out += 1;
+        }
         // TODO: lines and style sections contain identical line text
         if !self.minus_lines.is_empty() {
             Painter::paint_lines(
                 minus_line_syntax_style_sections,
                 minus_line_diff_style_sections,
+                minus_line_numbers,
                 &mut self.output_buffer,
                 self.config,
                 self.config.minus_line_marker,
@@ -88,6 +105,7 @@ impl<'a> Painter<'a> {
             Painter::paint_lines(
                 plus_line_syntax_style_sections,
                 plus_line_diff_style_sections,
+                plus_line_numbers,
                 &mut self.output_buffer,
                 self.config,
                 self.config.plus_line_marker,
@@ -104,6 +122,7 @@ impl<'a> Painter<'a> {
     pub fn paint_lines(
         syntax_style_sections: Vec<Vec<(Style, &str)>>,
         diff_style_sections: Vec<Vec<(StyleModifier, &str)>>,
+        line_number_sections: Vec<String>,
         output_buffer: &mut String,
         config: &config::Config,
         prefix: &str,
@@ -112,8 +131,11 @@ impl<'a> Painter<'a> {
     ) {
         let background_style = config.no_style.apply(background_style_modifier);
         let background_ansi_style = to_ansi_style(background_style, config.true_color);
-        for (syntax_sections, diff_sections) in
-            syntax_style_sections.iter().zip(diff_style_sections.iter())
+
+        for ((syntax_sections, diff_sections), line_numbers) in
+            syntax_style_sections.iter()
+                .zip(diff_style_sections.iter())
+                .zip(line_number_sections.iter())
         {
             let mut ansi_strings = Vec::new();
             if prefix != "" {
@@ -144,6 +166,10 @@ impl<'a> Painter<'a> {
                 {
                     line.truncate(line.len() - ANSI_SGR_RESET.len());
                 }
+
+                if config.show_line_numbers {
+                    output_buffer.push_str(&line_numbers);
+                }
                 output_buffer.push_str(&line);
                 output_buffer.push_str(ANSI_CSI_ERASE_IN_LINE);
                 output_buffer.push_str(ANSI_SGR_RESET);

src/parse.rs

@@ -71,14 +71,17 @@ pub fn get_file_change_description_from_file_paths(
 /// Given input like
 /// "@@ -74,15 +74,14 @@ pub fn delta("
 /// Return " pub fn delta("
-pub fn parse_hunk_metadata(line: &str) -> (&str, &str) {
+pub fn parse_hunk_metadata(line: &str) -> (&str, &str, &str) {
     let mut iter = line.split("@@").skip(1);
-    let line_number = iter
-        .next()
+    let line_number_iter = iter.next();
+    let line_number_in = line_number_iter
+        .and_then(|s| s.split('-').nth(1).and_then(|s| s.split(',').next()))
+        .unwrap_or("");
+    let line_number_out = line_number_iter
         .and_then(|s| s.split('+').nth(1).and_then(|s| s.split(',').next()))
         .unwrap_or("");
     let code_fragment = iter.next().unwrap_or("");
-    (code_fragment, line_number)
+    (code_fragment, line_number_in, line_number_out)
 }
 
 /// Given input like "diff --git a/src/main.rs b/src/main.rs"
@@ -216,7 +219,7 @@ mod tests {
     fn test_parse_hunk_metadata() {
         assert_eq!(
             parse_hunk_metadata("@@ -74,15 +75,14 @@ pub fn delta(\n"),
-            (" pub fn delta(\n", "75")
+            (" pub fn delta(\n", "74", "75")
         );
     }
 }