Merge branch 'fix/mvp-blockers'

Resolve test file conflict by keeping both sides. Fix lint warnings
in watcher_test.go (errcheck, gosec) from the merged branch.

Author: Astro-Han

internal/git/diff.go

@@ -17,6 +17,12 @@ func ComputeDiff(repoDir, baselineSHA string) ([]internal.FileDiff, error) {
 	if err != nil {
 		return nil, fmt.Errorf("git diff: %w", err)
 	}
+	if baselineSHA == EmptyTreeSHA {
+		tracked, err = overlayFreshRepoWorktreeChanges(repoDir, tracked)
+		if err != nil {
+			return nil, fmt.Errorf("git diff worktree: %w", err)
+		}
+	}
 
 	untracked, err := getUntrackedDiff(repoDir)
 	if err != nil {
@@ -61,6 +67,45 @@ func getTrackedDiff(repoDir, baselineSHA string) ([]internal.FileDiff, error) {
 	return ParseDiff(string(out)), nil
 }
 
+// overlayFreshRepoWorktreeChanges replaces cached added-file diffs with the
+// current worktree content for unborn-repo paths that were edited after staging.
+func overlayFreshRepoWorktreeChanges(repoDir string, tracked []internal.FileDiff) ([]internal.FileDiff, error) {
+	cmd := exec.Command("git", "diff", "--name-only", "-z", "--")
+	cmd.Dir = repoDir
+	out, err := cmd.Output()
+	if err != nil {
+		return nil, err
+	}
+
+	indexByPath := make(map[string]int, len(tracked))
+	result := append([]internal.FileDiff(nil), tracked...)
+	for i, file := range result {
+		indexByPath[file.Path] = i
+	}
+
+	for _, path := range strings.Split(string(out), "\x00") {
+		if path == "" {
+			continue
+		}
+
+		// #nosec G304 -- path comes from git diff output scoped to the repository.
+		data, readErr := os.ReadFile(filepath.Join(repoDir, path))
+		if readErr != nil {
+			continue
+		}
+
+		diff := buildNewFileDiff(path, string(data))
+		if idx, ok := indexByPath[path]; ok {
+			result[idx] = diff
+			continue
+		}
+		indexByPath[path] = len(result)
+		result = append(result, diff)
+	}
+
+	return result, nil
+}
+
 // getUntrackedDiff expands untracked files and directories to synthetic added diffs.
 // TODO(v2): reads entire file into memory; consider capping read size for large
 // generated files and delegating binary detection to git.

internal/git/diff_test.go

@@ -130,6 +130,39 @@ func TestComputeDiffFreshRepoUntrackedFile(t *testing.T) {
 	}
 }
 
+// TestComputeDiffFreshRepoStagedThenModifiedFile verifies an unborn repo shows
+// the current worktree content even after a file was staged earlier.
+func TestComputeDiffFreshRepoStagedThenModifiedFile(t *testing.T) {
+	root := initGitRepo(t)
+
+	baseline, err := GetHeadSHA(root)
+	if err != nil {
+		t.Fatalf("GetHeadSHA returned error: %v", err)
+	}
+	path := filepath.Join(root, "fresh.txt")
+	if err := os.WriteFile(path, []byte("a\n"), 0o600); err != nil {
+		t.Fatalf("write staged file: %v", err)
+	}
+	runGit(t, root, "add", "fresh.txt")
+	if err := os.WriteFile(path, []byte("b\n"), 0o600); err != nil {
+		t.Fatalf("rewrite worktree file: %v", err)
+	}
+
+	files, err := ComputeDiff(root, baseline)
+	if err != nil {
+		t.Fatalf("ComputeDiff returned error: %v", err)
+	}
+	if len(files) != 1 || files[0].Path != "fresh.txt" {
+		t.Fatalf("expected 1 file fresh.txt, got %#v", files)
+	}
+	if len(files[0].Hunks) != 1 || len(files[0].Hunks[0].Lines) != 1 {
+		t.Fatalf("unexpected hunks: %#v", files[0].Hunks)
+	}
+	if files[0].Hunks[0].Lines[0].Content != "b" {
+		t.Fatalf("line content = %q, want current worktree content", files[0].Hunks[0].Lines[0].Content)
+	}
+}
+
 // TestComputeDiffUntrackedFilePreservesInnerBlankLines verifies synthetic diffs
 // keep blank lines inside file content instead of dropping them.
 func TestComputeDiffUntrackedFilePreservesInnerBlankLines(t *testing.T) {

internal/ui/footer.go

@@ -3,14 +3,14 @@ package ui
 import "fmt"
 
 // RenderFooter renders the one-line footer or a transient notification.
-func RenderFooter(followOn bool, notification string) string {
+func RenderFooter(followOn bool, notification string, width int) string {
 	if notification != "" {
-		return StyleAdd.Render(notification)
+		return clampInlineWidth(StyleAdd.Render(notification), width)
 	}
 
 	status := "on"
 	if !followOn {
 		status = "off"
 	}
-	return StyleDim.Render(fmt.Sprintf("q quit · n/p files · f follow: %s · tab list", status))
+	return clampInlineWidth(StyleDim.Render(fmt.Sprintf("q quit · n/p files · f follow: %s · tab list", status)), width)
 }

internal/ui/header.go

@@ -8,9 +8,9 @@ import (
 )
 
 // RenderHeader renders the single-line top bar.
-func RenderHeader(dirName string, files []internal.FileDiff, currentIdx, newCount int) string {
+func RenderHeader(dirName string, files []internal.FileDiff, currentIdx, newCount, width int) string {
 	if len(files) == 0 {
-		return StyleDim.Render(fmt.Sprintf("%s · watching", dirName))
+		return clampInlineWidth(StyleDim.Render(fmt.Sprintf("%s · watching", dirName)), width)
 	}
 
 	currentIdx = min(max(currentIdx, 0), len(files)-1)
@@ -30,7 +30,7 @@ func RenderHeader(dirName string, files []internal.FileDiff, currentIdx, newCoun
 		result += "  " + StyleAdd.Render(fmt.Sprintf("+%d new", newCount))
 	}
 
-	return result
+	return clampInlineWidth(result, width)
 }
 
 // renderFileStats formats one file's change summary for header and overlay views.

internal/ui/header_test.go

@@ -9,7 +9,7 @@ import (
 
 // TestRenderHeaderEmpty verifies the empty state header shows directory and watching state.
 func TestRenderHeaderEmpty(t *testing.T) {
-	header := RenderHeader("myproject", nil, 0, 0)
+	header := RenderHeader("myproject", nil, 0, 0, 80)
 	if !strings.Contains(header, "myproject") || !strings.Contains(header, "watching") {
 		t.Fatalf("header = %q, want dir name and watching", header)
 	}
@@ -18,7 +18,7 @@ func TestRenderHeaderEmpty(t *testing.T) {
 // TestRenderHeaderSingleFile verifies one file does not show the file counter.
 func TestRenderHeaderSingleFile(t *testing.T) {
 	files := []internal.FileDiff{{Path: "src/auth.ts", AddCount: 3, DelCount: 1}}
-	header := RenderHeader("myproject", files, 0, 0)
+	header := RenderHeader("myproject", files, 0, 0, 80)
 	if strings.Contains(header, "›") {
 		t.Fatalf("single file header should not show counter, got %q", header)
 	}
@@ -30,7 +30,7 @@ func TestRenderHeaderMultipleFiles(t *testing.T) {
 		{Path: "src/auth.ts", AddCount: 3},
 		{Path: "src/utils.ts", AddCount: 1},
 	}
-	header := RenderHeader("myproject", files, 0, 0)
+	header := RenderHeader("myproject", files, 0, 0, 80)
 	if !strings.Contains(header, "1/2") {
 		t.Fatalf("header = %q, want counter 1/2", header)
 	}
@@ -39,7 +39,7 @@ func TestRenderHeaderMultipleFiles(t *testing.T) {
 // TestRenderHeaderNewCount verifies paused follow mode shows the pending new count.
 func TestRenderHeaderNewCount(t *testing.T) {
 	files := []internal.FileDiff{{Path: "a.ts", AddCount: 1}}
-	header := RenderHeader("myproject", files, 0, 3)
+	header := RenderHeader("myproject", files, 0, 3, 80)
 	if !strings.Contains(header, "+3 new") {
 		t.Fatalf("header = %q, want +3 new", header)
 	}
@@ -55,7 +55,7 @@ func TestRenderHeaderOutOfRangeIndex(t *testing.T) {
 		}
 	}()
 
-	header := RenderHeader("myproject", files, 9, 0)
+	header := RenderHeader("myproject", files, 9, 0, 80)
 	if !strings.Contains(header, "a.ts") {
 		t.Fatalf("header = %q, want file path", header)
 	}

internal/ui/model.go

@@ -90,6 +90,7 @@ func (m Model) handleFilesUpdated(msg FilesUpdatedMsg) (tea.Model, tea.Cmd) {
 		if m.PendingUpdate == nil {
 			m.PendingUpdate = &msg
 		} else {
+			m.PendingUpdate.BaselineSHA = msg.BaselineSHA
 			m.PendingUpdate.Files = msg.Files
 			m.PendingUpdate.ChangedPaths = append(m.PendingUpdate.ChangedPaths, msg.ChangedPaths...)
 		}
@@ -144,12 +145,24 @@ func (m Model) applyFilesUpdate(msg FilesUpdatedMsg) Model {
 		m.LastChangedPath = ""
 		m.NewCount = 0
 	} else if !m.FollowOn {
+		presentPaths := make(map[string]bool, len(m.Files))
+		for _, file := range m.Files {
+			presentPaths[file.Path] = true
+		}
+		for path := range m.NewFiles {
+			if !presentPaths[path] || path == currentPath {
+				delete(m.NewFiles, path)
+			}
+		}
 		for _, changedPath := range msg.ChangedPaths {
-			if changedPath != currentPath {
+			if changedPath != currentPath && presentPaths[changedPath] {
 				m.NewFiles[changedPath] = true
 				m.LastChangedPath = changedPath
 			}
 		}
+		if m.LastChangedPath != "" && !m.NewFiles[m.LastChangedPath] {
+			m.LastChangedPath = ""
+		}
 		m.NewCount = len(m.NewFiles)
 
 		found := false
@@ -333,12 +346,12 @@ func (m Model) View() string {
 	}
 
 	diffHeight := max(0, m.Height-2)
-	header := RenderHeader(m.DirName, m.Files, m.CurrentIdx, m.NewCount)
-	footer := RenderFooter(m.FollowOn, m.Notification)
+	header := RenderHeader(m.DirName, m.Files, m.CurrentIdx, m.NewCount, m.Width)
+	footer := RenderFooter(m.FollowOn, m.Notification, m.Width)
 
 	var content string
 	if m.OverlayOpen {
-		content = RenderOverlay(m.OverlaySnapshot, m.OverlayCursor, diffHeight)
+		content = RenderOverlay(m.OverlaySnapshot, m.OverlayCursor, diffHeight, m.Width)
 	} else if len(m.Files) > 0 && m.CurrentIdx < len(m.Files) {
 		content = RenderDiffView(&m.Files[m.CurrentIdx], m.ScrollOffset, m.Width, diffHeight)
 	}

internal/ui/model_test.go

@@ -6,6 +6,7 @@ import (
 
 	"github.com/Astro-Han/diffpane/internal"
 	tea "github.com/charmbracelet/bubbletea"
+	"github.com/charmbracelet/lipgloss"
 )
 
 func file(path string, adds int) internal.FileDiff {
@@ -91,6 +92,31 @@ func TestModelPausedFollowTracksNewFiles(t *testing.T) {
 	}
 }
 
+// TestModelPausedFollowIgnoresVanishedChangedPaths verifies transient changes
+// that disappear before the diff refresh lands do not inflate +N new.
+func TestModelPausedFollowIgnoresVanishedChangedPaths(t *testing.T) {
+	model := NewModel("repo", "/tmp/repo", "sha", []internal.FileDiff{
+		file("a.txt", 1),
+	})
+	model.FollowOn = false
+	model.CurrentIdx = 0
+
+	updated, _ := model.Update(FilesUpdatedMsg{
+		Files: []internal.FileDiff{
+			file("a.txt", 1),
+		},
+		ChangedPaths: []string{"temp.txt"},
+	})
+
+	got := updated.(Model)
+	if got.NewCount != 0 {
+		t.Fatalf("NewCount = %d, want 0", got.NewCount)
+	}
+	if len(got.NewFiles) != 0 {
+		t.Fatalf("NewFiles = %#v, want empty", got.NewFiles)
+	}
+}
+
 // TestModelOverlayQueuesUpdates verifies overlay mode freezes the view and applies pending updates on close.
 func TestModelOverlayQueuesUpdates(t *testing.T) {
 	model := NewModel("repo", "/tmp/repo", "sha", []internal.FileDiff{
@@ -281,6 +307,40 @@ func TestModelFollowClampsWhenCurrentFileDisappears(t *testing.T) {
 	}
 }
 
+// TestModelOverlayAppliesFreshUpdateAfterBaselineReset verifies a newer
+// baseline refresh still lands after overlay close, even if an old update was
+// queued earlier in the same overlay session.
+func TestModelOverlayAppliesFreshUpdateAfterBaselineReset(t *testing.T) {
+	model := NewModel("repo", "/tmp/repo", "old-sha", []internal.FileDiff{
+		file("old.txt", 1),
+	})
+
+	opened, _ := model.Update(tea.KeyMsg{Type: tea.KeyTab})
+	withOverlay := opened.(Model)
+
+	queuedOld, _ := withOverlay.Update(FilesUpdatedMsg{
+		BaselineSHA: "old-sha",
+		Files: []internal.FileDiff{
+			file("stale.txt", 1),
+		},
+		ChangedPaths: []string{"stale.txt"},
+	})
+	reset, _ := queuedOld.(Model).Update(BaselineResetMsg{NewSHA: "new-sha"})
+	queuedNew, _ := reset.(Model).Update(FilesUpdatedMsg{
+		BaselineSHA: "new-sha",
+		Files: []internal.FileDiff{
+			file("fresh.txt", 1),
+		},
+		ChangedPaths: []string{"fresh.txt"},
+	})
+	closed, _ := queuedNew.(Model).Update(tea.KeyMsg{Type: tea.KeyEsc})
+	got := closed.(Model)
+
+	if len(got.Files) != 1 || got.Files[0].Path != "fresh.txt" {
+		t.Fatalf("fresh overlay update should win after reset, got %#v", got.Files)
+	}
+}
+
 // TestModelViewSmallHeightDoesNotPanic verifies tiny terminal heights do not
 // trigger negative content heights in overlay rendering.
 func TestModelViewSmallHeightDoesNotPanic(t *testing.T) {
@@ -321,6 +381,54 @@ func TestModelViewEmptyStateFitsViewport(t *testing.T) {
 	}
 }
 
+// TestModelViewNarrowWidthKeepsChromeSingleLine verifies header and footer stay
+// within the viewport width instead of relying on terminal soft-wrap.
+func TestModelViewNarrowWidthKeepsChromeSingleLine(t *testing.T) {
+	model := NewModel("repo", "/tmp/repo", "sha", []internal.FileDiff{{
+		Path:     "very/long/path/to/current-file-name.ts",
+		AddCount: 12,
+		DelCount: 3,
+	}})
+	model.Width = 20
+	model.Height = 4
+
+	view := model.View()
+	lines := strings.Split(view, "\n")
+	if len(lines) != 4 {
+		t.Fatalf("line count = %d, want 4; view = %q", len(lines), view)
+	}
+	if lipgloss.Width(lines[0]) > model.Width {
+		t.Fatalf("header width = %d, want <= %d; header = %q", lipgloss.Width(lines[0]), model.Width, lines[0])
+	}
+	if lipgloss.Width(lines[3]) > model.Width {
+		t.Fatalf("footer width = %d, want <= %d; footer = %q", lipgloss.Width(lines[3]), model.Width, lines[3])
+	}
+}
+
+// TestModelOverlayNarrowWidthKeepsEntriesSingleLine verifies overlay rows fit
+// the viewport width instead of depending on soft-wrap.
+func TestModelOverlayNarrowWidthKeepsEntriesSingleLine(t *testing.T) {
+	model := NewModel("repo", "/tmp/repo", "sha", []internal.FileDiff{
+		{Path: "very/long/path/to/current-file-name.ts", AddCount: 12, DelCount: 3},
+		{Path: "another/extremely/long/path/to/second-file.ts", AddCount: 1},
+	})
+	model.Width = 20
+	model.Height = 4
+	model.OverlayOpen = true
+	model.OverlaySnapshot = append([]internal.FileDiff(nil), model.Files...)
+
+	view := model.View()
+	lines := strings.Split(view, "\n")
+	if len(lines) != 4 {
+		t.Fatalf("line count = %d, want 4; view = %q", len(lines), view)
+	}
+	for i := 1; i <= 2; i++ {
+		if lipgloss.Width(lines[i]) > model.Width {
+			t.Fatalf("overlay line %d width = %d, want <= %d; line = %q", i, lipgloss.Width(lines[i]), model.Width, lines[i])
+		}
+	}
+}
+
 // TestModelScrollOffsetStaysWithinContent verifies repeated down-navigation does
 // not grow scroll state beyond the visible diff content.
 func TestModelScrollOffsetStaysWithinContent(t *testing.T) {

internal/ui/overlay.go

@@ -8,9 +8,9 @@ import (
 )
 
 // RenderOverlay renders the frozen file list overlay.
-func RenderOverlay(files []internal.FileDiff, cursor, height int) string {
+func RenderOverlay(files []internal.FileDiff, cursor, height, width int) string {
 	if len(files) == 0 {
-		return StyleDim.Render("No changed files")
+		return clampInlineWidth(StyleDim.Render("No changed files"), width)
 	}
 
 	var lines []string
@@ -30,5 +30,8 @@ func RenderOverlay(files []internal.FileDiff, cursor, height int) string {
 	if end > len(lines) {
 		end = len(lines)
 	}
+	for i := start; i < end; i++ {
+		lines[i] = clampInlineWidth(lines[i], width)
+	}
 	return strings.Join(lines[start:end], "\n")
 }