diff: split hunks strictly by changes

Author: bohutang

packages/desktop/src/features/git/DiffManager.ts

@@ -37,7 +37,9 @@ export type WorkingTreeGroups = {
 const MAX_UNTRACKED_FILE_BYTES = 1024 * 1024; // 1MB
 
 export class GitDiffManager {
-  private readonly WORKING_DIFF_CONTEXT_LINES = 3; // Zed/Git default context
+  // Zed-like hunking: a hunk is only the contiguous changed lines.
+  // Any unchanged line should start a new hunk, so we request zero context from git.
+  private readonly WORKING_DIFF_CONTEXT_LINES = 0;
   constructor(
     private gitExecutor: GitExecutor,
     private logger?: Logger,

packages/desktop/src/features/git/StagingManager.ts

@@ -310,7 +310,7 @@ export class GitStagingManager {
     scope: 'staged' | 'unstaged',
     sessionId: string
   ): Promise<string> {
-    const unified = '--unified=3';
+    const unified = '--unified=0';
     const argv =
       scope === 'staged'
         ? ['git', 'diff', '--cached', '--color=never', unified, '--src-prefix=a/', '--dst-prefix=b/', 'HEAD', '--', filePath]

packages/desktop/src/features/git/__tests__/DiffManager.test.ts

@@ -3,7 +3,7 @@ import { GitDiffManager } from '../DiffManager';
 import type { GitExecutor } from '../../../executors/git';
 
 describe('GitDiffManager', () => {
-  it('uses --unified=3 for staged working tree diff', async () => {
+  it('uses --unified=0 for staged working tree diff', async () => {
     const mockGitExecutor: GitExecutor = {
       run: vi.fn(async ({ argv }) => {
         if (argv[1] === 'rev-parse') {
@@ -34,7 +34,7 @@ describe('GitDiffManager', () => {
       .mock.calls.find((c) => (c[0] as any).argv?.[1] === 'diff' && (c[0] as any).argv?.includes('--cached') && !(c[0] as any).argv?.includes('--name-only') && !(c[0] as any).argv?.includes('--shortstat'));
 
     expect(diffCall).toBeTruthy();
-    expect((diffCall?.[0] as any).argv).toEqual(expect.arrayContaining(['--unified=3']));
+    expect((diffCall?.[0] as any).argv).toEqual(expect.arrayContaining(['--unified=0']));
   });
 
   it('uses --unified=0 for commit diff (git show)', async () => {

packages/desktop/src/features/git/__tests__/StagingManager.test.ts

@@ -334,7 +334,7 @@ describe('GitStagingManager', () => {
 
       // Verify git diff was called
       expect(mockGitExecutor.run).toHaveBeenNthCalledWith(1, expect.objectContaining({
-        argv: expect.arrayContaining(['git', 'diff', '--unified=3']),
+        argv: expect.arrayContaining(['git', 'diff', '--unified=0']),
       }));
 
       // Verify git apply was called with --cached
@@ -683,7 +683,7 @@ Binary files differ`;
       expect(mockGitExecutor.run).toHaveBeenCalledTimes(2);
 
       expect(mockGitExecutor.run).toHaveBeenNthCalledWith(1, expect.objectContaining({
-        argv: expect.arrayContaining(['git', 'diff', '--cached', '--unified=3']),
+        argv: expect.arrayContaining(['git', 'diff', '--cached', '--unified=0']),
       }));
 
       expect(mockGitExecutor.run).toHaveBeenNthCalledWith(2, expect.objectContaining({
@@ -728,7 +728,7 @@ Binary files differ`;
       expect(result.success).toBe(true);
       expect(mockGitExecutor.run).toHaveBeenCalledTimes(2);
       expect(mockGitExecutor.run).toHaveBeenNthCalledWith(1, expect.objectContaining({
-        argv: expect.arrayContaining(['git', 'diff', '--unified=3']),
+        argv: expect.arrayContaining(['git', 'diff', '--unified=0']),
       }));
       expect(mockGitExecutor.run).toHaveBeenNthCalledWith(2, expect.objectContaining({
         argv: expect.arrayContaining(['git', 'apply', '-R']),
@@ -779,7 +779,7 @@ Binary files differ`;
       expect(result.success).toBe(true);
       expect(mockGitExecutor.run).toHaveBeenCalledTimes(3);
       expect(mockGitExecutor.run).toHaveBeenNthCalledWith(1, expect.objectContaining({
-        argv: expect.arrayContaining(['git', 'diff', '--cached', '--unified=3']),
+        argv: expect.arrayContaining(['git', 'diff', '--cached', '--unified=0']),
       }));
       expect(mockGitExecutor.run).toHaveBeenNthCalledWith(2, expect.objectContaining({
         argv: expect.arrayContaining(['git', 'apply', '--cached', '-R']),

packages/ui/src/components/panels/diff/ZedDiffViewer.test.tsx

@@ -47,6 +47,34 @@ describe('ZedDiffViewer', () => {
     expect(screen.getByTestId('diff-viewer-zed')).toBeInTheDocument();
   });
 
+  it('expands modified files to full file when fileSources is provided', () => {
+    const diff = `diff --git a/a.txt b/a.txt
+index 1234567..abcdefg 100644
+--- a/a.txt
++++ b/a.txt
+@@ -2,1 +2,1 @@
+-old
++new`;
+
+    const { container } = render(<ZedDiffViewer diff={diff} fileSources={{ 'a.txt': 'one\nold\nthree' }} />);
+    // one (context) + old (delete) + new (insert) + three (context)
+    expect(container.querySelectorAll('tr.diff-line')).toHaveLength(4);
+  });
+
+  it('does not duplicate content when expanding a new file diff', () => {
+    const diff = `diff --git a/new.txt b/new.txt
+new file mode 100644
+index 0000000..abcdefg
+--- /dev/null
++++ b/new.txt
+@@ -0,0 +1,2 @@
++first
++second`;
+
+    const { container } = render(<ZedDiffViewer diff={diff} fileSources={{ 'new.txt': 'first\nsecond' }} />);
+    expect(container.querySelectorAll('tr.diff-line')).toHaveLength(2);
+  });
+
   it('stages a hunk when scope is unstaged', async () => {
     (API.sessions.stageHunk as any).mockResolvedValue({ success: true, data: { success: true } });
     render(

packages/ui/src/components/panels/diff/ZedDiffViewer.tsx

@@ -76,6 +76,12 @@ function expandToFullFile(hunks: HunkData[], source: string): HunkData[] {
     return all ? [all] : [];
   }
 
+  // New file diffs typically use @@ -0,0 +1,N @@ and already contain the full content as insertions.
+  // Expanding using the worktree content would duplicate the file as "plain context" below the inserted hunk.
+  if (normalized.some((h) => h.oldStart === 0 && h.oldLines === 0)) {
+    return normalized;
+  }
+
   const output: HunkData[] = [];
   let oldCursor = 1;
   let delta = 0; // newLine = oldLine + delta for unchanged lines