Add side-by-side diff view

Closes #86

Cargo.toml

@@ -9,7 +9,7 @@ homepage = "https://github.com/dandavison/delta"
 license = "MIT"
 readme = "README.md"
 repository = "https://github.com/dandavison/delta"
-version = "0.2.1"
+version = "0.3.0"
 
 [[bin]]
 name = "delta"

src/cli.rs

@@ -212,6 +212,10 @@ pub struct Opt {
     #[structopt(short = "n", long = "line-numbers")]
     pub line_numbers: bool,
 
+    /// Display a side-by-side diff view instead of the traditional view.
+    #[structopt(long = "side-by-side")]
+    pub side_by_side: bool,
+
     #[structopt(long = "diff-highlight")]
     /// Emulate diff-highlight (https://github.com/git/git/tree/master/contrib/diff-highlight)
     pub diff_highlight: bool,
@@ -516,6 +520,7 @@ pub struct ComputedValues {
     pub syntax_theme: Option<SyntaxTheme>,
     pub syntax_dummy_theme: SyntaxTheme,
     pub true_color: bool,
+    pub available_terminal_width: usize,
     pub decorations_width: Width,
     pub background_color_extends_to_terminal_width: bool,
     pub paging_mode: PagingMode,

src/config.rs

@@ -12,9 +12,11 @@ use crate::cli;
 use crate::color;
 use crate::delta::State;
 use crate::env;
+use crate::features::side_by_side;
 use crate::style::Style;
 
 pub struct Config {
+    pub available_terminal_width: usize,
     pub background_color_extends_to_terminal_width: bool,
     pub commit_style: Style,
     pub decorations_width: cli::Width,
@@ -50,11 +52,14 @@ pub struct Config {
     pub plus_non_emph_style: Style,
     pub plus_style: Style,
     pub line_numbers: bool,
+    pub side_by_side: bool,
+    pub side_by_side_data: side_by_side::SideBySideData,
     pub syntax_dummy_theme: SyntaxTheme,
     pub syntax_set: SyntaxSet,
     pub syntax_theme: Option<SyntaxTheme>,
     pub tab_width: usize,
     pub true_color: bool,
+    pub truncation_symbol: String,
     pub tokenization_regex: Regex,
     pub whitespace_error_style: Style,
     pub zero_style: Style,
@@ -112,7 +117,13 @@ impl From<cli::Opt> for Config {
             process::exit(1);
         });
 
+        let side_by_side_data = side_by_side::SideBySideData::new(
+            &opt.computed.decorations_width,
+            &opt.computed.available_terminal_width,
+        );
+
         Self {
+            available_terminal_width: opt.computed.available_terminal_width,
             background_color_extends_to_terminal_width: opt
                 .computed
                 .background_color_extends_to_terminal_width,
@@ -150,12 +161,15 @@ impl From<cli::Opt> for Config {
             plus_non_emph_style,
             plus_style,
             line_numbers: opt.line_numbers,
+            side_by_side: opt.side_by_side,
+            side_by_side_data,
             syntax_dummy_theme: SyntaxTheme::default(),
             syntax_set: opt.computed.syntax_set,
             syntax_theme: opt.computed.syntax_theme,
             tab_width: opt.tab_width,
             tokenization_regex,
             true_color: opt.computed.true_color,
+            truncation_symbol: "→".to_string(),
             whitespace_error_style,
             zero_style,
         }

src/edits.rs

@@ -8,7 +8,8 @@ use crate::align;
 /// Infer the edit operations responsible for the differences between a collection of old and new
 /// lines. A "line" is a string. An annotated line is a Vec of (op, &str) pairs, where the &str
 /// slices are slices of the line, and their concatenation equals the line. Return the input minus
-/// and plus lines, in annotated form.
+/// and plus lines, in annotated form. Also return a specification of the inferred alignment of
+/// minus and plus lines.
 pub fn infer_edits<'a, EditOperation>(
     minus_lines: &'a [String],
     plus_lines: &'a [String],
@@ -20,19 +21,21 @@ pub fn infer_edits<'a, EditOperation>(
     max_line_distance: f64,
     max_line_distance_for_naively_paired_lines: f64,
 ) -> (
-    Vec<Vec<(EditOperation, &'a str)>>, // annotated minus lines
-    Vec<Vec<(EditOperation, &'a str)>>, // annotated plus lines
+    Vec<Vec<(EditOperation, &'a str)>>,  // annotated minus lines
+    Vec<Vec<(EditOperation, &'a str)>>,  // annotated plus lines
+    Vec<(Option<usize>, Option<usize>)>, // line alignment
 )
 where
     EditOperation: Copy,
     EditOperation: PartialEq,
 {
     let mut annotated_minus_lines = Vec::<Vec<(EditOperation, &str)>>::new();
     let mut annotated_plus_lines = Vec::<Vec<(EditOperation, &str)>>::new();
+    let mut line_alignment = Vec::<(Option<usize>, Option<usize>)>::new();
 
     let mut plus_index = 0; // plus lines emitted so far
 
-    'minus_lines_loop: for minus_line in minus_lines {
+    'minus_lines_loop: for (minus_index, minus_line) in minus_lines.iter().enumerate() {
         let mut considered = 0; // plus lines considered so far as match for minus_line
         for plus_line in &plus_lines[plus_index..] {
             let alignment = align::Alignment::new(
@@ -57,10 +60,12 @@ where
                 // Emit as unpaired the plus lines already considered and rejected
                 for plus_line in &plus_lines[plus_index..(plus_index + considered)] {
                     annotated_plus_lines.push(vec![(noop_insertion, plus_line)]);
+                    line_alignment.push((None, Some(plus_index)));
+                    plus_index += 1;
                 }
-                plus_index += considered;
                 annotated_minus_lines.push(annotated_minus_line);
                 annotated_plus_lines.push(annotated_plus_line);
+                line_alignment.push((Some(minus_index), Some(plus_index)));
                 plus_index += 1;
 
                 // Greedy: move on to the next minus line.
@@ -71,13 +76,16 @@ where
         }
         // No homolog was found for minus i; emit as unpaired.
         annotated_minus_lines.push(vec![(noop_deletion, minus_line)]);
+        line_alignment.push((Some(minus_index), None));
     }
     // Emit any remaining plus lines
     for plus_line in &plus_lines[plus_index..] {
         annotated_plus_lines.push(vec![(noop_insertion, plus_line)]);
+        line_alignment.push((None, Some(plus_index)));
+        plus_index += 1;
     }
 
-    (annotated_minus_lines, annotated_plus_lines)
+    (annotated_minus_lines, annotated_plus_lines, line_alignment)
 }
 
 /// Split line into tokens for alignment. The alignment algorithm aligns sequences of substrings;
@@ -736,7 +744,8 @@ mod tests {
             0.0,
         );
         // compare_annotated_lines(actual_edits, expected_edits);
-        assert_eq!(actual_edits, expected_edits);
+        // TODO: test line alignment
+        assert_eq!((actual_edits.0, actual_edits.1), expected_edits);
     }
 
     // Assert that no edits are inferred for the supplied minus and plus lines.

src/features/line_numbers.rs

@@ -6,6 +6,7 @@ use regex::Regex;
 
 use crate::config;
 use crate::delta::State;
+use crate::features::side_by_side;
 use crate::features::OptionValueFunction;
 use crate::style::Style;
 
@@ -63,6 +64,7 @@ pub fn make_feature() -> Vec<(String, OptionValueFunction)> {
 pub fn format_and_paint_line_numbers<'a>(
     line_numbers_data: &'a mut LineNumbersData,
     state: &State,
+    side_by_side_panel: Option<side_by_side::PanelSide>,
     config: &'a config::Config,
 ) -> Vec<ansi_term::ANSIGenericString<'a, str>> {
     let m_ref = &mut line_numbers_data.hunk_minus_line_number;
@@ -94,25 +96,36 @@ pub fn format_and_paint_line_numbers<'a>(
 
     let mut formatted_numbers = Vec::new();
 
-    formatted_numbers.extend(format_and_paint_line_number_field(
-        &line_numbers_data.left_format_data,
-        &config.line_numbers_left_style,
-        minus_number,
-        plus_number,
-        line_numbers_data.hunk_max_line_number_width,
-        &minus_style,
-        &plus_style,
-    ));
-    formatted_numbers.extend(format_and_paint_line_number_field(
-        &line_numbers_data.right_format_data,
-        &config.line_numbers_right_style,
-        minus_number,
-        plus_number,
-        line_numbers_data.hunk_max_line_number_width,
-        &minus_style,
-        &plus_style,
-    ));
+    let (emit_left, emit_right) = match (config.side_by_side, side_by_side_panel) {
+        (false, _) => (true, true),
+        (true, Some(side_by_side::PanelSide::Left)) => (true, false),
+        (true, Some(side_by_side::PanelSide::Right)) => (false, true),
+        (true, None) => unreachable!(),
+    };
+
+    if emit_left {
+        formatted_numbers.extend(format_and_paint_line_number_field(
+            &line_numbers_data.left_format_data,
+            &config.line_numbers_left_style,
+            minus_number,
+            plus_number,
+            line_numbers_data.hunk_max_line_number_width,
+            &minus_style,
+            &plus_style,
+        ));
+    }
 
+    if emit_right {
+        formatted_numbers.extend(format_and_paint_line_number_field(
+            &line_numbers_data.right_format_data,
+            &config.line_numbers_right_style,
+            minus_number,
+            plus_number,
+            line_numbers_data.hunk_max_line_number_width,
+            &minus_style,
+            &plus_style,
+        ));
+    }
     formatted_numbers
 }
 
@@ -506,7 +519,7 @@ pub mod tests {
         assert_eq!(lines.next().unwrap(), "     ⋮10000│bb = 2");
     }
 
-    const TWO_MINUS_LINES_DIFF: &str = "\
+    pub const TWO_MINUS_LINES_DIFF: &str = "\
 diff --git i/a.py w/a.py
 index 223ca50..e69de29 100644
 --- i/a.py
@@ -516,7 +529,7 @@ index 223ca50..e69de29 100644
 -b = 2
 ";
 
-    const TWO_PLUS_LINES_DIFF: &str = "\
+    pub const TWO_PLUS_LINES_DIFF: &str = "\
 diff --git c/a.py i/a.py
 new file mode 100644
 index 0000000..223ca50
@@ -527,7 +540,7 @@ index 0000000..223ca50
 +b = 2
 ";
 
-    const ONE_MINUS_ONE_PLUS_LINE_DIFF: &str = "\
+    pub const ONE_MINUS_ONE_PLUS_LINE_DIFF: &str = "\
 diff --git i/a.py w/a.py
 index 223ca50..367a6f6 100644
 --- i/a.py

src/features/mod.rs

@@ -47,6 +47,10 @@ pub fn make_builtin_features() -> HashMap<String, BuiltinFeature> {
             navigate::make_feature().into_iter().collect(),
         ),
         ("raw".to_string(), raw::make_feature().into_iter().collect()),
+        (
+            "side-by-side".to_string(),
+            side_by_side::make_feature().into_iter().collect(),
+        ),
     ]
     .into_iter()
     .collect()
@@ -80,6 +84,7 @@ pub mod diff_so_fancy;
 pub mod line_numbers;
 pub mod navigate;
 pub mod raw;
+pub mod side_by_side;
 
 #[cfg(test)]
 pub mod tests {