Add --keep-plus-minus-markers option

Makefile

@@ -6,13 +6,14 @@ lint:
 
 test:
 	cargo test
-	bash -c "diff -u <(git log -p | cut -c 2-) \
+	bash -c "diff -u <(git log -p) \
                      <(git log -p | delta --width variable \
                                           --tabs 0 \
+                                          --keep-plus-minus-markers \
                                           --commit-style plain \
                                           --file-style plain \
                                           --hunk-style plain \
-                                  | ansifilter | cut -c 2-)"
+                                  | ansifilter)"
 
 release:
 	@make -f release.Makefile release

completion/bash/completion.sh

@@ -31,6 +31,7 @@ _delta() {
         --minus-emph-color
         --plus-color
         --plus-emph-color
+        --keep-plus-minus-markers
         --show-background-colors
         --theme
         --version

src/cli.rs

@@ -97,6 +97,11 @@ pub struct Opt {
     /// apply syntax highlighting to unchanged and new lines only.
     pub highlight_removed: bool,
 
+    #[structopt(long = "keep-plus-minus-markers")]
+    /// Prefix added/removed lines with a +/- character, respectively, exactly as git does. The
+    /// default behavior is to output a space character in place of these markers.
+    pub keep_plus_minus_markers: bool,
+
     #[structopt(long = "commit-style", default_value = "plain")]
     /// Formatting style for the commit section of git output. Options
     /// are: plain, box.

src/config.rs

@@ -18,6 +18,8 @@ pub struct Config<'a> {
     pub minus_emph_style_modifier: StyleModifier,
     pub plus_style_modifier: StyleModifier,
     pub plus_emph_style_modifier: StyleModifier,
+    pub minus_line_marker: &'a str,
+    pub plus_line_marker: &'a str,
     pub highlight_removed: bool,
     pub commit_style: cli::SectionStyle,
     pub commit_color: Color,
@@ -102,6 +104,17 @@ pub fn get_config<'a>(
         font_style: None,
     };
 
+    let minus_line_marker = if opt.keep_plus_minus_markers {
+        "-"
+    } else {
+        " "
+    };
+    let plus_line_marker = if opt.keep_plus_minus_markers {
+        "+"
+    } else {
+        " "
+    };
+
     Config {
         theme,
         theme_name,
@@ -111,6 +124,8 @@ pub fn get_config<'a>(
         plus_style_modifier,
         plus_emph_style_modifier,
         highlight_removed: opt.highlight_removed,
+        minus_line_marker,
+        plus_line_marker,
         commit_style: opt.commit_style,
         commit_color: color_from_rgb_or_ansi_code(&opt.commit_color),
         file_style: opt.file_style,

src/delta.rs

@@ -271,6 +271,7 @@ fn handle_hunk_meta_line(
             )]],
             &mut painter.output_buffer,
             config,
+            "",
             style::NO_BACKGROUND_COLOR_STYLE_MODIFIER,
             false,
         );
@@ -321,6 +322,7 @@ fn handle_hunk_line(painter: &mut Painter, line: &str, state: State, config: &Co
             State::HunkPlus
         }
         _ => {
+            let is_empty = line.is_empty();
             painter.paint_buffered_lines();
             let line = prepare(&line, true, config);
             let syntax_style_sections = Painter::get_line_syntax_style_sections(
@@ -334,6 +336,7 @@ fn handle_hunk_line(painter: &mut Painter, line: &str, state: State, config: &Co
                 vec![vec![(style::NO_BACKGROUND_COLOR_STYLE_MODIFIER, &line)]],
                 &mut painter.output_buffer,
                 config,
+                if is_empty { "" } else { " " },
                 style::NO_BACKGROUND_COLOR_STYLE_MODIFIER,
                 true,
             );
@@ -352,8 +355,9 @@ fn prepare(line: &str, append_newline: bool, config: &Config) -> String {
     if !line.is_empty() {
         let mut line = line.graphemes(true);
 
-        // The first column contains a -/+/space character, added by git. We skip it here and insert
-        // a replacement space when formatting the line below.
+        // The first column contains a -/+/space character, added by git. We drop it now, so that
+        // it is not present during syntax highlighting, and inject a replacement when emitting the
+        // line.
         line.next();
 
         // Expand tabs as spaces.
@@ -365,7 +369,7 @@ fn prepare(line: &str, append_newline: bool, config: &Config) -> String {
         } else {
             line.collect::<String>()
         };
-        format!(" {}{}", output_line, terminator)
+        format!("{}{}", output_line, terminator)
     } else {
         terminator.to_string()
     }
@@ -604,6 +608,7 @@ mod tests {
             minus_emph_color: None,
             plus_color: None,
             plus_emph_color: None,
+            keep_plus_minus_markers: false,
             theme: None,
             highlight_removed: false,
             commit_style: cli::SectionStyle::Plain,

src/paint.rs

@@ -77,6 +77,7 @@ impl<'a> Painter<'a> {
                 minus_line_diff_style_sections,
                 &mut self.output_buffer,
                 self.config,
+                self.config.minus_line_marker,
                 self.config.minus_style_modifier,
                 true,
             );
@@ -87,6 +88,7 @@ impl<'a> Painter<'a> {
                 plus_line_diff_style_sections,
                 &mut self.output_buffer,
                 self.config,
+                self.config.plus_line_marker,
                 self.config.plus_style_modifier,
                 true,
             );
@@ -102,14 +104,20 @@ impl<'a> Painter<'a> {
         diff_style_sections: Vec<Vec<(StyleModifier, &str)>>,
         output_buffer: &mut String,
         config: &config::Config,
+        prefix: &str,
         background_style_modifier: StyleModifier,
         should_trim_newline_and_right_pad: bool,
     ) {
+        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())
         {
             let mut text_width = 0;
             let mut ansi_strings = Vec::new();
+            if prefix != "" {
+                ansi_strings.push(background_ansi_style.paint(prefix));
+            }
             for (style, text) in superimpose_style_sections(syntax_sections, diff_sections) {
                 if config.width.is_some() {
                     text_width += text.graphemes(true).count();
@@ -122,7 +130,6 @@ impl<'a> Painter<'a> {
                 match config.width {
                     Some(width) if width > text_width => {
                         // Right pad to requested width with spaces.
-                        let background_style = config.no_style.apply(background_style_modifier);
                         paint_text(
                             &" ".repeat(width - text_width),
                             background_style,