Merge 5cf6719003 into 8619c07f3f

CHANGELOG.md

@@ -10,10 +10,12 @@ and this project adheres to [Semantic Versioning](https://semver.org/spec/v2.0.0
 ### Changed
 * use [tombi](https://github.com/tombi-toml/tombi) for all toml file formatting
 * open the external editor from the status diff view [[@WaterWhisperer](https://github.com/WaterWhisperer)] ([#2805](https://github.com/gitui-org/gitui/issues/2805))
+* change diff mode toggle shortcut from `Alt+p` to `m`
 
 ### Fixes
 * crash when opening submodule ([#2895](https://github.com/gitui-org/gitui/issues/2895))
 * when staging the last file in a directory, the first item after the directory is no longer skipped [[@Tillerino](https://github.com/Tillerino)] ([#2748](https://github.com/gitui-org/gitui/issues/2748))
+* fixed duplicated "Toggle Diff Mode" in help message
 
 ## [0.28.1] - 2026-03-21
 

src/components/diff.rs

@@ -23,14 +23,27 @@ use asyncgit::{
 use bytesize::ByteSize;
 use crossterm::event::Event;
 use ratatui::{
-	layout::Rect,
+	layout::{
+		Constraint, Direction as RatatuiDirection, Layout, Rect,
+	},
 	symbols,
 	text::{Line, Span},
 	widgets::{Block, Borders, Paragraph},
 	Frame,
 };
+use serde::{Deserialize, Serialize};
 use std::{borrow::Cow, cell::Cell, cmp, path::Path};
 
+/// Diff display mode
+#[derive(
+	Default, Clone, Copy, PartialEq, Eq, Serialize, Deserialize,
+)]
+pub enum DiffMode {
+	#[default]
+	Unified,
+	SideBySide,
+}
+
 #[derive(Default)]
 struct Current {
 	path: String,
@@ -101,6 +114,24 @@ impl Selection {
 	}
 }
 
+/// A single line in side-by-side diff view
+struct SideBySideLine {
+	left_content: String,
+	left_line_num: Option<u32>,
+	right_content: String,
+	right_line_num: Option<u32>,
+	left_type: DiffLineType,
+	right_type: DiffLineType,
+	/// Global line index for selection tracking
+	global_line_idx: usize,
+	/// Index of the hunk this line belongs to
+	hunk_idx: usize,
+	/// Whether this is the first line of a hunk
+	is_hunk_start: bool,
+	/// Whether this is the last line of a hunk
+	is_hunk_end: bool,
+}
+
 ///
 pub struct DiffComponent {
 	repo: RepoPathRef,
@@ -119,6 +150,7 @@ pub struct DiffComponent {
 	key_config: SharedKeyConfig,
 	is_immutable: bool,
 	options: SharedOptions,
+	diff_mode: DiffMode,
 }
 
 impl DiffComponent {
@@ -141,6 +173,7 @@ impl DiffComponent {
 			is_immutable,
 			repo: env.repo.clone(),
 			options: env.options.clone(),
+			diff_mode: env.options.borrow().diff_mode(),
 		}
 	}
 	///
@@ -223,11 +256,19 @@ impl DiffComponent {
 
 	fn move_selection(&mut self, move_type: ScrollType) {
 		if let Some(diff) = &self.diff {
-			let max = diff.lines.saturating_sub(1);
+			// In side-by-side mode, display lines differ from diff.lines
+			// because Delete+Add pairs are shown as one line
+			let max = if self.diff_mode == DiffMode::SideBySide {
+				self.side_by_side_lines_count().saturating_sub(1)
+			} else {
+				diff.lines.saturating_sub(1)
+			};
 
 			let new_start = match move_type {
 				ScrollType::Down => {
-					self.selection.get_bottom().saturating_add(1)
+					let next =
+						self.selection.get_bottom().saturating_add(1);
+					cmp::min(next, max)
 				}
 				ScrollType::Up => {
 					self.selection.get_top().saturating_sub(1)
@@ -235,10 +276,14 @@ impl DiffComponent {
 				ScrollType::Home => 0,
 				ScrollType::End => max,
 				ScrollType::PageDown => {
-					self.selection.get_bottom().saturating_add(
+					let next =
-						self.current_size.get().1.saturating_sub(1)
+						self.selection.get_bottom().saturating_add(
-							as usize,
+							self.current_size
-					)
+								.get()
+								.1
+								.saturating_sub(1) as usize,
+						);
+					cmp::min(next, max)
 				}
 				ScrollType::PageUp => {
 					self.selection.get_top().saturating_sub(
@@ -254,11 +299,20 @@ impl DiffComponent {
 
 	fn update_selection(&mut self, new_start: usize) {
 		if let Some(diff) = &self.diff {
-			let max = diff.lines.saturating_sub(1);
+			// In side-by-side mode, display lines differ from diff.lines
+			let max = if self.diff_mode == DiffMode::SideBySide {
+				self.side_by_side_lines_count().saturating_sub(1)
+			} else {
+				diff.lines.saturating_sub(1)
+			};
 			let new_start = cmp::min(max, new_start);
 			self.selection = Selection::Single(new_start);
 			self.selected_hunk =
-				Self::find_selected_hunk(diff, new_start);
+				Self::find_selected_hunk_for_display_line(
+					diff,
+					new_start,
+					self.diff_mode,
+				);
 		}
 	}
 
@@ -266,9 +320,52 @@ impl DiffComponent {
 		self.diff.as_ref().map_or(0, |diff| diff.lines)
 	}
 
+	/// Get the actual display line count for side-by-side mode
+	/// In side-by-side mode, Delete+Add pairs are shown as one line
+	fn side_by_side_lines_count(&self) -> usize {
+		let Some(diff) = &self.diff else {
+			return 0;
+		};
+
+		if diff.hunks.is_empty() {
+			return 0;
+		}
+
+		let mut count = 0_usize;
+		for hunk in &diff.hunks {
+			let mut i = 0;
+			while i < hunk.lines.len() {
+				let line = &hunk.lines[i];
+				if line.line_type == DiffLineType::Delete {
+					// Check if next line is Add (they will be paired)
+					if let Some(next) = hunk.lines.get(i + 1) {
+						if next.line_type == DiffLineType::Add {
+							i += 1; // Skip the Add line in counting
+						}
+					}
+				}
+				count += 1;
+				i += 1;
+			}
+		}
+
+		count
+	}
+
 	fn max_scroll_right(&self) -> usize {
-		self.longest_line
+		let available_width: usize = if self.diff_mode
-			.saturating_sub(self.current_size.get().0.into())
+			== DiffMode::SideBySide
+		{
+			// In side-by-side mode, each panel's content width:
+			// chunks[0].width ≈ r.width / 2
+			// content width = chunks[0].width - 7 (border + marker + line_num + space)
+			// current_width = r.width - 2
+			// So: r.width / 2 - 7 ≈ current_width / 2 - 6
+			(self.current_size.get().0 / 2).saturating_sub(6).into()
+		} else {
+			self.current_size.get().0.into()
+		};
+		self.longest_line.saturating_sub(available_width)
 	}
 
 	fn modify_selection(&mut self, direction: Direction) {
@@ -328,6 +425,50 @@ impl DiffComponent {
 		None
 	}
 
+	/// Find the hunk index for a display line (accounting for side-by-side pairing)
+	fn find_selected_hunk_for_display_line(
+		diff: &FileDiff,
+		display_line_selected: usize,
+		diff_mode: DiffMode,
+	) -> Option<usize> {
+		if diff_mode == DiffMode::Unified {
+			return Self::find_selected_hunk(
+				diff,
+				display_line_selected,
+			);
+		}
+
+		// For side-by-side mode, count display lines (where Delete+Add pairs count as 1)
+		let mut display_cursor = 0_usize;
+		for (i, hunk) in diff.hunks.iter().enumerate() {
+			let mut j = 0;
+			let hunk_start = display_cursor;
+			while j < hunk.lines.len() {
+				let line = &hunk.lines[j];
+				if display_cursor == display_line_selected {
+					return Some(i);
+				}
+				if line.line_type == DiffLineType::Delete {
+					if let Some(next) = hunk.lines.get(j + 1) {
+						if next.line_type == DiffLineType::Add {
+							j += 1;
+						}
+					}
+				}
+				display_cursor += 1;
+				j += 1;
+			}
+			// Check if this is the last line of the hunk
+			if display_line_selected >= hunk_start
+				&& display_line_selected < display_cursor
+			{
+				return Some(i);
+			}
+		}
+
+		None
+	}
+
 	fn get_text(&self, width: u16, height: u16) -> Vec<Line<'_>> {
 		if let Some(diff) = &self.diff {
 			return if diff.hunks.is_empty() {
@@ -677,6 +818,485 @@ impl DiffComponent {
 		}
 	}
 
+	/// Toggle between unified and side-by-side diff mode
+	pub fn toggle_diff_mode(&mut self) {
+		self.diff_mode = match self.diff_mode {
+			DiffMode::Unified => DiffMode::SideBySide,
+			DiffMode::SideBySide => DiffMode::Unified,
+		};
+		self.options.borrow_mut().set_diff_mode(self.diff_mode);
+	}
+
+	fn get_side_by_side_lines(
+		&self,
+		height: u16,
+	) -> Vec<SideBySideLine> {
+		let Some(diff) = &self.diff else {
+			return Vec::new();
+		};
+
+		if diff.hunks.is_empty() {
+			return Vec::new();
+		}
+
+		let min = self.vertical_scroll.get_top();
+		let max = min + height as usize;
+
+		let mut result = Vec::new();
+		// Use display_cursor to track display line index (where Delete+Add pairs count as 1)
+		let mut display_cursor = 0_usize;
+
+		for (hunk_idx, hunk) in diff.hunks.iter().enumerate() {
+			// Calculate display line range for this hunk
+			let hunk_display_start = display_cursor;
+			let mut hunk_display_len = 0_usize;
+			{
+				let mut j = 0;
+				while j < hunk.lines.len() {
+					let line = &hunk.lines[j];
+					if line.line_type == DiffLineType::Delete {
+						if let Some(next) = hunk.lines.get(j + 1) {
+							if next.line_type == DiffLineType::Add {
+								j += 1;
+							}
+						}
+					}
+					hunk_display_len += 1;
+					j += 1;
+				}
+			}
+			let hunk_display_end =
+				hunk_display_start + hunk_display_len;
+
+			if Self::hunk_visible(
+				hunk_display_start,
+				hunk_display_end,
+				min,
+				max,
+			) {
+				let mut i = 0;
+				while i < hunk.lines.len() {
+					let line = &hunk.lines[i];
+					let global_display_idx = display_cursor;
+					let is_hunk_start = i == 0;
+					// Calculate if this is the last display line of the hunk
+					let is_hunk_end = {
+						let mut remaining = hunk.lines.len() - i;
+						let next = hunk.lines.get(i + 1);
+						if line.line_type == DiffLineType::Delete
+							&& next.is_some_and(|n| {
+								n.line_type == DiffLineType::Add
+							}) {
+							remaining -= 1;
+						}
+						remaining == 1
+					};
+
+					if global_display_idx >= min
+						&& global_display_idx <= max
+					{
+						match line.line_type {
+							DiffLineType::Delete => {
+								// Look ahead for a matching add line
+								let next_line = hunk.lines.get(i + 1);
+								let (
+									right_content,
+									right_num,
+									right_type,
+								) = if let Some(next) = next_line {
+									if next.line_type
+										== DiffLineType::Add
+									{
+										i += 1;
+										(
+											tabs_to_spaces(
+												next.content
+													.as_ref()
+													.to_string(),
+											),
+											next.position.new_lineno,
+											DiffLineType::Add,
+										)
+									} else {
+										(
+											String::new(),
+											None,
+											DiffLineType::None,
+										)
+									}
+								} else {
+									(
+										String::new(),
+										None,
+										DiffLineType::None,
+									)
+								};
+
+								result.push(SideBySideLine {
+									left_content: tabs_to_spaces(
+										line.content
+											.as_ref()
+											.to_string(),
+									),
+									left_line_num: line
+										.position
+										.old_lineno,
+									right_content,
+									right_line_num: right_num,
+									left_type: DiffLineType::Delete,
+									right_type,
+									global_line_idx:
+										global_display_idx,
+									hunk_idx,
+									is_hunk_start,
+									is_hunk_end,
+								});
+							}
+							DiffLineType::Add => {
+								// Add line not paired with a delete
+								result.push(SideBySideLine {
+									left_content: String::new(),
+									left_line_num: None,
+									right_content: tabs_to_spaces(
+										line.content
+											.as_ref()
+											.to_string(),
+									),
+									right_line_num: line
+										.position
+										.new_lineno,
+									left_type: DiffLineType::None,
+									right_type: DiffLineType::Add,
+									global_line_idx:
+										global_display_idx,
+									hunk_idx,
+									is_hunk_start,
+									is_hunk_end,
+								});
+							}
+							DiffLineType::Header => {
+								let header_content = tabs_to_spaces(
+									line.content.as_ref().to_string(),
+								);
+								result.push(SideBySideLine {
+									left_content: header_content,
+									left_line_num: None,
+									right_content: String::new(),
+									right_line_num: None,
+									left_type: DiffLineType::Header,
+									right_type: DiffLineType::Header,
+									global_line_idx:
+										global_display_idx,
+									hunk_idx,
+									is_hunk_start,
+									is_hunk_end,
+								});
+							}
+							DiffLineType::None => {
+								// Context line - appears in both columns
+								result.push(SideBySideLine {
+									left_content: tabs_to_spaces(
+										line.content
+											.as_ref()
+											.to_string(),
+									),
+									left_line_num: line
+										.position
+										.old_lineno,
+									right_content: tabs_to_spaces(
+										line.content
+											.as_ref()
+											.to_string(),
+									),
+									right_line_num: line
+										.position
+										.new_lineno,
+									left_type: DiffLineType::None,
+									right_type: DiffLineType::None,
+									global_line_idx:
+										global_display_idx,
+									hunk_idx,
+									is_hunk_start,
+									is_hunk_end,
+								});
+							}
+						}
+					}
+
+					// Increment display cursor for each display line
+					display_cursor += 1;
+					i += 1;
+				}
+			} else {
+				// Skip this hunk's display lines
+				display_cursor += hunk_display_len;
+			}
+		}
+
+		result
+	}
+
+	fn draw_side_by_side(
+		&self,
+		f: &mut Frame,
+		r: Rect,
+		title: &str,
+		height: u16,
+	) -> Result<()> {
+		// Split area into left and right columns
+		let chunks = Layout::default()
+			.direction(RatatuiDirection::Horizontal)
+			.constraints(
+				[
+					Constraint::Percentage(50),
+					Constraint::Percentage(50),
+				]
+				.as_ref(),
+			)
+			.split(r);
+
+		// Calculate available width for content (subtract borders, marker, line number, space)
+		// Each panel has: 1 border + 1 marker + 4 line num + 1 space = 7 chars overhead
+		let panel_width = chunks[0].width.saturating_sub(7) as usize;
+
+		let lines = self.get_side_by_side_lines(height);
+		let scrolled_right = self.horizontal_scroll.get_right();
+		let selected_hunk = self.selected_hunk;
+
+		// Get current selection index
+		let current_selection = self.selection.get_end();
+
+		// Build left column text with selection highlighting
+		let left_txt: Vec<Line> = lines
+			.iter()
+			.map(|line| {
+				let selected = self.focused()
+					&& line.global_line_idx == current_selection;
+				let hunk_selected = self.focused()
+					&& selected_hunk
+						.is_some_and(|h| h == line.hunk_idx);
+				let left_content =
+					trim_offset(&line.left_content, scrolled_right);
+				let line_num_str = line
+					.left_line_num
+					.map_or(String::from("    "), |n| {
+						format!("{n:4}")
+					});
+
+				// Get hunk marker style
+				let marker_style =
+					self.theme.diff_hunk_marker(hunk_selected);
+				let marker = if line.is_hunk_end {
+					symbols::line::BOTTOM_LEFT
+				} else if line.is_hunk_start {
+					symbols::line::TOP_LEFT
+				} else {
+					symbols::line::VERTICAL
+				};
+
+				// Pad content to fill width when selected
+				let content = if selected {
+					format!("{:w$}\n", left_content, w = panel_width)
+				} else {
+					format!("{left_content}\n")
+				};
+
+				// For lines where left side is empty (e.g., Add lines without Delete pair),
+				// still apply selection highlight to maintain visual consistency.
+				// Show line_break symbol (¶) for empty Add/Delete lines, same as unified mode.
+				if line.left_content.is_empty() {
+					// Show line_break symbol for empty Add/Delete lines
+					let display_content =
+						if line.left_type != DiffLineType::None {
+							self.theme.line_break()
+						} else {
+							String::new()
+						};
+					let content = if selected {
+						format!(
+							"{:w$}\n",
+							display_content,
+							w = panel_width
+						)
+					} else {
+						format!("{display_content}\n")
+					};
+					Line::from(vec![
+						Span::styled(Cow::from(marker), marker_style),
+						Span::styled(
+							Cow::from(line_num_str),
+							self.theme.text(false, false),
+						),
+						// Gap - never highlighted
+						Span::styled(
+							Cow::from(" "),
+							self.theme.text(false, false),
+						),
+						Span::styled(
+							Cow::from(content),
+							self.theme
+								.diff_line(line.left_type, selected),
+						),
+					])
+				} else {
+					Line::from(vec![
+						Span::styled(Cow::from(marker), marker_style),
+						Span::styled(
+							Cow::from(line_num_str),
+							self.theme.text(false, false),
+						),
+						// Gap between line number and content - never highlighted
+						Span::styled(
+							Cow::from(" "),
+							self.theme.text(false, false),
+						),
+						Span::styled(
+							Cow::from(content),
+							self.theme
+								.diff_line(line.left_type, selected),
+						),
+					])
+				}
+			})
+			.collect();
+
+		// Build right column text with selection highlighting
+		let right_txt: Vec<Line> = lines
+			.iter()
+			.map(|line| {
+				let selected = self.focused()
+					&& line.global_line_idx == current_selection;
+				let hunk_selected = self.focused()
+					&& selected_hunk
+						.is_some_and(|h| h == line.hunk_idx);
+				let right_content =
+					trim_offset(&line.right_content, scrolled_right);
+				let line_num_str = line
+					.right_line_num
+					.map_or(String::from("    "), |n| {
+						format!("{n:4}")
+					});
+
+				// Get hunk marker style
+				let marker_style =
+					self.theme.diff_hunk_marker(hunk_selected);
+				let marker = if line.is_hunk_end {
+					symbols::line::BOTTOM_LEFT
+				} else if line.is_hunk_start {
+					symbols::line::TOP_LEFT
+				} else {
+					symbols::line::VERTICAL
+				};
+
+				// Pad content to fill width when selected
+				let content = if selected {
+					format!("{:w$}\n", right_content, w = panel_width)
+				} else {
+					format!("{right_content}\n")
+				};
+
+				// For lines where right side is empty (Header or paired Delete),
+				// still apply selection highlight to maintain visual consistency.
+				// Show line_break symbol (¶) for empty Add/Delete lines, same as unified mode.
+				if line.right_type == DiffLineType::Header
+					|| line.right_content.is_empty()
+				{
+					// Show line_break symbol for empty Add/Delete lines (but not Header)
+					let display_content = if line.right_type
+						!= DiffLineType::None
+						&& line.right_type != DiffLineType::Header
+					{
+						self.theme.line_break()
+					} else {
+						String::new()
+					};
+					let filler = if selected {
+						format!(
+							"{:w$}\n",
+							display_content,
+							w = panel_width
+						)
+					} else {
+						format!("{display_content}\n")
+					};
+					Line::from(vec![
+						Span::styled(Cow::from(marker), marker_style),
+						Span::styled(
+							Cow::from(line_num_str),
+							self.theme.text(false, false),
+						),
+						// Gap - never highlighted
+						Span::styled(
+							Cow::from(" "),
+							self.theme.text(false, false),
+						),
+						Span::styled(
+							Cow::from(filler),
+							self.theme
+								.diff_line(line.right_type, selected),
+						),
+					])
+				} else {
+					Line::from(vec![
+						Span::styled(Cow::from(marker), marker_style),
+						Span::styled(
+							Cow::from(line_num_str),
+							self.theme.text(false, false),
+						),
+						// Gap between line number and content - never highlighted
+						Span::styled(
+							Cow::from(" "),
+							self.theme.text(false, false),
+						),
+						Span::styled(
+							Cow::from(content),
+							self.theme
+								.diff_line(line.right_type, selected),
+						),
+					])
+				}
+			})
+			.collect();
+
+		// Draw left column
+		f.render_widget(
+			Paragraph::new(left_txt).block(
+				Block::default()
+					.title(Span::styled(
+						format!("{title} [Old]"),
+						self.theme.title(self.focused()),
+					))
+					.borders(Borders::ALL)
+					.border_style(self.theme.block(self.focused())),
+			),
+			chunks[0],
+		);
+
+		// Draw right column
+		f.render_widget(
+			Paragraph::new(right_txt).block(
+				Block::default()
+					.title(Span::styled(
+						"[New]",
+						self.theme.title(self.focused()),
+					))
+					.borders(Borders::ALL)
+					.border_style(self.theme.block(self.focused())),
+			),
+			chunks[1],
+		);
+
+		if self.focused() {
+			self.vertical_scroll.draw(f, r, &self.theme);
+
+			if self.max_scroll_right() > 0 {
+				self.horizontal_scroll.draw(f, r, &self.theme);
+			}
+		}
+
+		Ok(())
+	}
+
 	const fn is_stage(&self) -> bool {
 		self.current.is_stage
 	}
@@ -692,15 +1312,32 @@ impl DrawableComponent for DiffComponent {
 		let current_width = self.current_size.get().0;
 		let current_height = self.current_size.get().1;
 
+		// Use display line count for side-by-side mode
+		let lines_count = if self.diff_mode == DiffMode::SideBySide {
+			self.side_by_side_lines_count()
+		} else {
+			self.lines_count()
+		};
+
 		self.vertical_scroll.update(
 			self.selection.get_end(),
-			self.lines_count(),
+			lines_count,
 			usize::from(current_height),
 		);
 
+		// In side-by-side mode, each panel content width is smaller
+		// chunks[0].width ≈ r.width / 2, content = chunks[0].width - 7
+		// ≈ current_width / 2 - 6
+		let panel_content_width: usize =
+			if self.diff_mode == DiffMode::SideBySide {
+				(current_width / 2).saturating_sub(6).into()
+			} else {
+				current_width.into()
+			};
+
 		self.horizontal_scroll.update_no_selection(
 			self.longest_line,
-			current_width.into(),
+			panel_content_width,
 		);
 
 		let title = format!(
@@ -709,33 +1346,41 @@ impl DrawableComponent for DiffComponent {
 			self.current.path
 		);
 
-		let txt = if self.pending {
+		if self.diff_mode == DiffMode::SideBySide && !self.pending {
-			vec![Line::from(vec![Span::styled(
+			self.draw_side_by_side(f, r, &title, current_height)?;
-				Cow::from(strings::loading_text(&self.key_config)),
-				self.theme.text(false, false),
-			)])]
 		} else {
-			self.get_text(r.width, current_height)
+			let txt = if self.pending {
-		};
+				vec![Line::from(vec![Span::styled(
+					Cow::from(strings::loading_text(
+						&self.key_config,
+					)),
+					self.theme.text(false, false),
+				)])]
+			} else {
+				self.get_text(r.width, current_height)
+			};
 
-		f.render_widget(
+			f.render_widget(
-			Paragraph::new(txt).block(
+				Paragraph::new(txt).block(
-				Block::default()
+					Block::default()
-					.title(Span::styled(
+						.title(Span::styled(
-						title.as_str(),
+							title.as_str(),
-						self.theme.title(self.focused()),
+							self.theme.title(self.focused()),
-					))
+						))
-					.borders(Borders::ALL)
+						.borders(Borders::ALL)
-					.border_style(self.theme.block(self.focused())),
+						.border_style(
-			),
+							self.theme.block(self.focused()),
-			r,
+						),
-		);
+				),
+				r,
+			);
 
-		if self.focused() {
+			if self.focused() {
-			self.vertical_scroll.draw(f, r, &self.theme);
+				self.vertical_scroll.draw(f, r, &self.theme);
 
-			if self.max_scroll_right() > 0 {
+				if self.max_scroll_right() > 0 {
-				self.horizontal_scroll.draw(f, r, &self.theme);
+					self.horizontal_scroll.draw(f, r, &self.theme);
+				}
 			}
 		}
 
@@ -943,6 +1588,12 @@ impl Component for DiffComponent {
 				} else if key_match(e, self.key_config.keys.copy) {
 					self.copy_selection();
 					Ok(EventState::Consumed)
+				} else if key_match(
+					e,
+					self.key_config.keys.diff_mode_toggle,
+				) {
+					self.toggle_diff_mode();
+					Ok(EventState::Consumed)
 				} else {
 					Ok(EventState::NotConsumed)
 				};
@@ -1059,4 +1710,35 @@ mod tests {
 				if path == "src/main.rs"
 		));
 	}
+
+	#[test]
+	fn test_commands_no_longer_contains_toggle_diff() {
+		let env = Environment::test_env();
+		let diff = DiffComponent::new(&env, false);
+		let mut cmds = Vec::new();
+		diff.commands(&mut cmds, true);
+
+		let contains_toggle = cmds.iter().any(|c| {
+			c.text.name
+				== strings::commands::diff_toggle_mode(&env.key_config)
+					.name
+		});
+		assert!(!contains_toggle);
+	}
+
+	#[test]
+	fn test_diff_mode_toggle_event() {
+		let env = Environment::test_env();
+		let mut diff = DiffComponent::new(&env, false);
+		diff.focus(true);
+
+		let event = Event::Key(KeyEvent::from(
+			&env.key_config.keys.diff_mode_toggle,
+		));
+
+		assert!(matches!(
+			diff.event(&event).unwrap(),
+			EventState::Consumed
+		));
+	}
 }

src/components/mod.rs

@@ -53,7 +53,7 @@ pub use command::{CommandInfo, CommandText};
 pub use commit_details::CommitDetailsComponent;
 pub use commitlist::CommitList;
 pub use cred::CredComponent;
-pub use diff::DiffComponent;
+pub use diff::{DiffComponent, DiffMode};
 pub use revision_files::RevisionFilesComponent;
 pub use syntax_text::SyntaxTextComponent;
 pub use textinput::{InputType, TextInputComponent};

src/keys/key_list.rs

@@ -129,6 +129,7 @@ pub struct KeysList {
 	pub commit: GituiKeyEvent,
 	pub newline: GituiKeyEvent,
 	pub goto_line: GituiKeyEvent,
+	pub diff_mode_toggle: GituiKeyEvent,
 }
 
 #[rustfmt::skip]
@@ -227,6 +228,7 @@ impl Default for KeysList {
 			commit: GituiKeyEvent::new(KeyCode::Char('d'),  KeyModifiers::CONTROL),
 			newline: GituiKeyEvent::new(KeyCode::Enter,  KeyModifiers::empty()),
 			goto_line: GituiKeyEvent::new(KeyCode::Char('L'),  KeyModifiers::SHIFT),
+			diff_mode_toggle: GituiKeyEvent::new(KeyCode::Char('m'),  KeyModifiers::empty()),
 		}
 	}
 }

src/options.rs

@@ -1,3 +1,4 @@
+use crate::components::DiffMode;
 use anyhow::Result;
 use asyncgit::sync::{
 	diff::DiffOptions, repo_dir, RepoPathRef,
@@ -22,6 +23,7 @@ struct OptionsData {
 	pub diff: DiffOptions,
 	pub status_show_untracked: Option<ShowUntrackedFilesConfig>,
 	pub commit_msgs: Vec<String>,
+	pub diff_mode: DiffMode,
 }
 
 const COMMIT_MSG_HISTORY_LENGTH: usize = 20;
@@ -107,6 +109,15 @@ impl Options {
 		self.save();
 	}
 
+	pub const fn diff_mode(&self) -> DiffMode {
+		self.data.diff_mode
+	}
+
+	pub fn set_diff_mode(&mut self, mode: DiffMode) {
+		self.data.diff_mode = mode;
+		self.save();
+	}
+
 	pub fn add_commit_msg(&mut self, msg: &str) {
 		self.data.commit_msgs.push(msg.to_owned());
 		while self.data.commit_msgs.len() > COMMIT_MSG_HISTORY_LENGTH

src/popups/compare_commits.rs

@@ -95,6 +95,12 @@ impl Component for CompareCommitsPopup {
 				!self.diff.focused() || force_all,
 			));
 
+			out.push(CommandInfo::new(
+				strings::commands::diff_toggle_mode(&self.key_config),
+				true,
+				true,
+			));
+
 			out.push(CommandInfo::new(
 				strings::commands::diff_focus_left(&self.key_config),
 				true,
@@ -134,6 +140,11 @@ impl Component for CompareCommitsPopup {
 				} else if key_match(e, self.key_config.keys.move_left)
 				{
 					self.hide_stacked(false);
+				} else if key_match(
+					e,
+					self.key_config.keys.diff_mode_toggle,
+				) {
+					self.diff.toggle_diff_mode();
 				}
 
 				return Ok(EventState::Consumed);

src/popups/file_revlog.rs

@@ -569,6 +569,11 @@ impl Component for FileRevlogPopup {
 					self.key_config.keys.page_down,
 				) {
 					self.move_selection(ScrollType::PageDown)?;
+				} else if key_match(
+					key,
+					self.key_config.keys.diff_mode_toggle,
+				) {
+					self.diff.toggle_diff_mode();
 				}
 			}
 
@@ -610,6 +615,11 @@ impl Component for FileRevlogPopup {
 				)
 				.order(1),
 			);
+			out.push(CommandInfo::new(
+				strings::commands::diff_toggle_mode(&self.key_config),
+				true,
+				true,
+			));
 
 			out.push(CommandInfo::new(
 				strings::commands::diff_focus_right(&self.key_config),

src/popups/inspect_commit.rs

@@ -136,6 +136,12 @@ impl Component for InspectCommitPopup {
 				true,
 				true,
 			));
+
+			out.push(CommandInfo::new(
+				strings::commands::diff_toggle_mode(&self.key_config),
+				true,
+				true,
+			));
 		}
 
 		visibility_blocking(self)
@@ -171,6 +177,11 @@ impl Component for InspectCommitPopup {
 				} else if key_match(e, self.key_config.keys.move_left)
 				{
 					self.hide_stacked(false);
+				} else if key_match(
+					e,
+					self.key_config.keys.diff_mode_toggle,
+				) {
+					self.diff.toggle_diff_mode();
 				} else if key_match(
 					e,
 					self.key_config.keys.open_file_tree,

src/strings.rs

@@ -834,6 +834,18 @@ pub mod commands {
 			CMD_GROUP_DIFF,
 		)
 	}
+	pub fn diff_toggle_mode(
+		key_config: &SharedKeyConfig,
+	) -> CommandText {
+		CommandText::new(
+			format!(
+				"Toggle Diff Mode [{}]",
+				key_config.get_hint(key_config.keys.diff_mode_toggle),
+			),
+			"toggle between unified and side-by-side diff",
+			CMD_GROUP_DIFF,
+		)
+	}
 	pub fn close_fuzzy_finder(
 		key_config: &SharedKeyConfig,
 	) -> CommandText {

src/tabs/status.rs

@@ -804,6 +804,12 @@ impl Component for Status {
 				true,
 				true,
 			));
+
+			out.push(CommandInfo::new(
+				strings::commands::diff_toggle_mode(&self.key_config),
+				true,
+				true,
+			));
 		}
 
 		self.commands_nav(out, force_all);
@@ -947,6 +953,12 @@ impl Component for Status {
 				) {
 					self.queue.push(InternalEvent::ViewSubmodules);
 					Ok(EventState::Consumed)
+				} else if key_match(
+					k,
+					self.key_config.keys.diff_mode_toggle,
+				) {
+					self.diff.toggle_diff_mode();
+					Ok(EventState::Consumed)
 				} else {
 					Ok(EventState::NotConsumed)
 				};

vim_style_key_config.ron

@@ -31,6 +31,9 @@
     diff_reset_lines: Some(( code: Char('u'), modifiers: "")),
     diff_stage_lines: Some(( code: Char('s'), modifiers: "")),
 
+    // toggle between unified and side-by-side diff mode
+    diff_mode_toggle: Some(( code: Char('m'), modifiers: "")),
+
     stashing_save: Some(( code: Char('w'), modifiers: "")),
     stashing_toggle_index: Some(( code: Char('m'), modifiers: "")),