feat: support dynamic target

cmd/difi/main.go

@@ -1,6 +1,7 @@
 package main
 
 import (
+	"flag"
 	"fmt"
 	"os"
 
@@ -10,14 +11,39 @@ import (
 )
 
 func main() {
-	// Load config (defaults used if file missing)
+	// Define flags
+	help := flag.Bool("help", false, "Show help")
+	flag.Usage = func() {
+		fmt.Fprintf(os.Stderr, "Usage: difi [flags] [target-branch]\n")
+		fmt.Fprintf(os.Stderr, "\nFlags:\n")
+		flag.PrintDefaults()
+		fmt.Fprintf(os.Stderr, "\nExamples:\n")
+		fmt.Fprintf(os.Stderr, "  difi             # Diff against main\n")
+		fmt.Fprintf(os.Stderr, "  difi develop     # Diff against develop\n")
+		fmt.Fprintf(os.Stderr, "  difi HEAD~1      # Diff against last commit\n")
+	}
+	flag.Parse()
+
+	if *help {
+		flag.Usage()
+		os.Exit(0)
+	}
+
+	// Determine Target Branch
+	// If user provides an argument (e.g., "difi develop"), use it.
+	// Otherwise default to "main".
+	target := "main"
+	if flag.NArg() > 0 {
+		target = flag.Arg(0)
+	}
+
+	// Load Config
 	cfg := config.Load()
 
-	// Pass config to model
-	p := tea.NewProgram(ui.NewModel(cfg), tea.WithAltScreen())
-
+	// Pass target to the model
+	p := tea.NewProgram(ui.NewModel(cfg, target), tea.WithAltScreen())
 	if _, err := p.Run(); err != nil {
-		fmt.Printf("Error running difi: %v", err)
+		fmt.Printf("Error: %v\n", err)
 		os.Exit(1)
 	}
 }

internal/ui/model.go

@@ -17,7 +17,7 @@ import (
 	"github.com/oug-t/difi/internal/tree"
 )
 
-const TargetBranch = "main"
+// REMOVED: const TargetBranch = "main" (Now dynamic)
 
 type Focus int
 
@@ -33,6 +33,7 @@ type Model struct {
 
 	selectedPath  string
 	currentBranch string
+	targetBranch  string // Added field for dynamic target
 	repoName      string
 
 	diffContent string
@@ -47,10 +48,12 @@ type Model struct {
 	width, height int
 }
 
-func NewModel(cfg config.Config) Model {
+// Updated Signature: Accepts targetBranch string
+func NewModel(cfg config.Config, targetBranch string) Model {
 	InitStyles(cfg)
 
-	files, _ := git.ListChangedFiles(TargetBranch)
+	// Use the dynamic targetBranch variable
+	files, _ := git.ListChangedFiles(targetBranch)
 	items := tree.Build(files)
 
 	delegate := TreeDelegate{Focused: true}
@@ -69,6 +72,7 @@ func NewModel(cfg config.Config) Model {
 		diffViewport:  viewport.New(0, 0),
 		focus:         FocusTree,
 		currentBranch: git.GetCurrentBranch(),
+		targetBranch:  targetBranch, // Store it
 		repoName:      git.GetRepoName(),
 		showHelp:      false,
 		inputBuffer:   "",
@@ -84,7 +88,8 @@ func NewModel(cfg config.Config) Model {
 
 func (m Model) Init() tea.Cmd {
 	if m.selectedPath != "" {
-		return git.DiffCmd(TargetBranch, m.selectedPath)
+		// Use m.targetBranch instead of constant
+		return git.DiffCmd(m.targetBranch, m.selectedPath)
 	}
 	return nil
 }
@@ -211,7 +216,8 @@ func (m Model) Update(msg tea.Msg) (tea.Model, tea.Cmd) {
 				m.selectedPath = item.FullPath
 				m.diffCursor = 0
 				m.diffViewport.GotoTop()
-				cmds = append(cmds, git.DiffCmd(TargetBranch, m.selectedPath))
+				// Use m.targetBranch
+				cmds = append(cmds, git.DiffCmd(m.targetBranch, m.selectedPath))
 			}
 		}
 	}
@@ -223,7 +229,8 @@ func (m Model) Update(msg tea.Msg) (tea.Model, tea.Cmd) {
 		m.diffViewport.SetContent(msg.Content)
 
 	case git.EditorFinishedMsg:
-		return m, git.DiffCmd(TargetBranch, m.selectedPath)
+		// Use m.targetBranch
+		return m, git.DiffCmd(m.targetBranch, m.selectedPath)
 	}
 
 	return m, tea.Batch(cmds...)
@@ -260,7 +267,6 @@ func (m Model) View() string {
 		return "Loading..."
 	}
 
-	// 1. PANES
 	treeStyle := PaneStyle
 	if m.focus == FocusTree {
 		treeStyle = FocusedPaneStyle
@@ -280,11 +286,9 @@ func (m Model) View() string {
 		end = len(m.diffLines)
 	}
 
-	// RENDER LOOP
 	for i := start; i < end; i++ {
 		line := m.diffLines[i]
 
-		// --- LINE NUMBERS ---
 		var numStr string
 		mode := CurrentConfig.UI.LineNumbers
 
@@ -310,7 +314,6 @@ func (m Model) View() string {
 			lineNumRendered = LineNumberStyle.Render(numStr)
 		}
 
-		// --- DIFF VIEW HIGHLIGHT ---
 		if m.focus == FocusDiff && i == m.diffCursor {
 			cleanLine := stripAnsi(line)
 			line = DiffSelectionStyle.Render("  " + cleanLine)
@@ -328,11 +331,11 @@ func (m Model) View() string {
 
 	mainPanes := lipgloss.JoinHorizontal(lipgloss.Top, treeView, diffView)
 
-	// 2. BOTTOM AREA
 	repoSection := StatusKeyStyle.Render(" " + m.repoName)
 	divider := StatusDividerStyle.Render("│")
 
-	statusText := fmt.Sprintf(" %s ↔ %s", m.currentBranch, TargetBranch)
+	// Use m.targetBranch in status bar
+	statusText := fmt.Sprintf(" %s ↔ %s", m.currentBranch, m.targetBranch)
 	if m.inputBuffer != "" {
 		statusText += fmt.Sprintf(" [Cmd: %s]", m.inputBuffer)
 	}