feat: add --unified flag

go.mod

@@ -10,6 +10,7 @@ require (
 	github.com/charmbracelet/log v0.4.0
 	github.com/charmbracelet/x/ansi v0.3.2
 	github.com/muesli/reflow v0.3.0
+	github.com/urfave/cli/v3 v3.3.8
 )
 
 require (

go.sum

@@ -51,6 +51,8 @@ github.com/rivo/uniseg v0.4.7 h1:WUdvkW8uEhrYfLC4ZzdpI2ztxP1I582+49Oc5Mq64VQ=
 github.com/rivo/uniseg v0.4.7/go.mod h1:FN3SvrM+Zdj16jyLfmOkMNblXMcoc8DfTHruCPUcx88=
 github.com/stretchr/testify v1.9.0 h1:HtqpIVDClZ4nwg75+f6Lvsy/wHu+3BoSGCbBAcpTsTg=
 github.com/stretchr/testify v1.9.0/go.mod h1:r2ic/lqez/lEtzL7wO/rwa5dbSLXVDPFyf8C91i36aY=
+github.com/urfave/cli/v3 v3.3.8 h1:BzolUExliMdet9NlJ/u4m5vHSotJ3PzEqSAZ1oPMa/E=
+github.com/urfave/cli/v3 v3.3.8/go.mod h1:FJSKtM/9AiiTOJL4fJ6TbMUkxBXn7GO9guZqoZtpYpo=
 golang.org/x/exp v0.0.0-20231006140011-7918f672742d h1:jtJma62tbqLibJ5sFQz8bKtEM8rJBtfilJ2qTU199MI=
 golang.org/x/exp v0.0.0-20231006140011-7918f672742d/go.mod h1:ldy0pHrwJyGW56pPQzzkH36rKxoZW1tw7ZJpeKx+hdo=
 golang.org/x/sync v0.8.0 h1:3NFvSEYkUoMifnESzZl15y791HH1qU2xm6eCJU5ZPXQ=

main.go

@@ -2,6 +2,7 @@ package main
 
 import (
 	"bufio"
+	"context"
 	"fmt"
 	"io"
 	"os"
@@ -12,22 +13,45 @@ import (
 	"github.com/charmbracelet/log"
 	"github.com/charmbracelet/x/ansi"
 	"github.com/muesli/termenv"
+	"github.com/urfave/cli/v3"
 
 	"github.com/dlvhdr/diffnav/pkg/ui"
 )
 
 func main() {
+	cmd := &cli.Command{
+		Usage: "A git diff pager with a file tree",
+		Flags: []cli.Flag{
+			&cli.BoolFlag{
+				Name:        "unified",
+				Aliases:     []string{"u"},
+				Usage:       "side-by-side (default) or unified diff",
+				HideDefault: true,
+			},
+			&cli.BoolFlag{
+				Name:    "debug",
+				Usage:   "log to debug.log",
+				Sources: cli.EnvVars("DEBUG"),
+			},
+		},
+		Action: runDiffNav,
+	}
+	if err := cmd.Run(context.Background(), os.Args); err != nil {
+		log.Fatal(err)
+	}
+}
+
+func runDiffNav(ctx context.Context, cmd *cli.Command) error {
 	stat, err := os.Stdin.Stat()
 	if err != nil {
 		panic(err)
 	}
-
 	if stat.Mode()&os.ModeNamedPipe == 0 && stat.Size() == 0 {
 		fmt.Println("No diff, exiting")
 		os.Exit(0)
 	}
 
-	if os.Getenv("DEBUG") == "true" {
+	if cmd.Bool("debug") {
 		var fileErr error
 		logFile, fileErr := os.OpenFile("debug.log", os.O_RDWR|os.O_CREATE|os.O_APPEND, 0666)
 		if fileErr != nil {
@@ -73,9 +97,8 @@ func main() {
 		fmt.Println("No input provided, exiting")
 		os.Exit(0)
 	}
-	p := tea.NewProgram(ui.New(input), tea.WithMouseAllMotion())
+	p := tea.NewProgram(ui.New(input, cmd.Bool("unified")), tea.WithMouseAllMotion())
 
-	if _, err := p.Run(); err != nil {
-		log.Fatal(err)
-	}
+	_, err = p.Run()
+	return err
 }

pkg/ui/mainModel.go

@@ -44,10 +44,10 @@ type mainModel struct {
 	filtered          []string
 }
 
-func New(input string) mainModel {
+func New(input string, unified bool) mainModel {
 	m := mainModel{input: input, isShowingFileTree: true}
 	m.fileTree = filetree.New()
-	m.diffViewer = diffviewer.New()
+	m.diffViewer = diffviewer.New(unified)
 
 	m.help = help.New()
 	helpSt := lipgloss.NewStyle()

pkg/ui/panes/diffviewer/diffviewer.go

@@ -19,14 +19,16 @@ const dirHeaderHeight = 3
 
 type Model struct {
 	common.Common
-	vp     viewport.Model
-	buffer *bytes.Buffer
-	file   *gitdiff.File
+	vp      viewport.Model
+	unified bool
+	buffer  *bytes.Buffer
+	file    *gitdiff.File
 }
 
-func New() Model {
+func New(unified bool) Model {
 	return Model{
-		vp: viewport.Model{},
+		vp:      viewport.Model{},
+		unified: unified,
 	}
 }
 
@@ -68,7 +70,7 @@ func (m *Model) SetSize(width, height int) tea.Cmd {
 	m.Height = height
 	m.vp.Width = m.Width
 	m.vp.Height = m.Height - dirHeaderHeight
-	return diff(m.file, m.Width)
+	return diff(m.file, m.Width, m.unified)
 }
 
 func (m Model) headerView() string {
@@ -109,19 +111,19 @@ func (m Model) headerView() string {
 func (m Model) SetFilePatch(file *gitdiff.File) (Model, tea.Cmd) {
 	m.buffer = new(bytes.Buffer)
 	m.file = file
-	return m, diff(m.file, m.Width)
+	return m, diff(m.file, m.Width, m.unified)
 }
 
 func (m *Model) GoToTop() {
 	m.vp.GotoTop()
 }
 
-func diff(file *gitdiff.File, width int) tea.Cmd {
+func diff(file *gitdiff.File, width int, unified bool) tea.Cmd {
 	if width == 0 || file == nil {
 		return nil
 	}
 	return func() tea.Msg {
-		sideBySide := !file.IsNew && !file.IsDelete
+		sideBySide := !unified && !file.IsNew && !file.IsDelete
 		args := []string{"--paging=never", fmt.Sprintf("-w=%d", width)}
 		if sideBySide {
 			args = append(args, "--side-by-side")