feat(actions-fleet): install planner with unified diff preview

packages/actions-fleet-core/src/diff/plan.ts

@@ -17,6 +17,8 @@ export interface PlannedFileDiff {
   mergeStrategy: PlannedFile['mergeStrategy'];
   newContent: string;
   newHash: string;
+  /** The content of the file as it exists on disk (or null if the file does not exist). */
+  existingContent: string | null;
   status: DiffStatus;
 }
 
@@ -170,6 +172,7 @@ export async function planDiff(options: PlanDiffOptions): Promise<DiffPlan> {
       mergeStrategy: file.mergeStrategy,
       newContent: file.content,
       newHash: file.hash,
+      existingContent: existing,
       status,
     });
   }

packages/actions-fleet-core/src/diff/render-diff.test.ts

@@ -0,0 +1,186 @@
+import { describe, it, expect } from 'vitest';
+import { createHash } from 'node:crypto';
+import { mkdtemp, rm } from 'node:fs/promises';
+import { tmpdir } from 'node:os';
+import { join } from 'node:path';
+import { renderUnifiedDiff, renderPlanPreview } from './render-diff.js';
+import { planDiff } from './plan.js';
+import type { RenderResult } from '../action-pack/render.js';
+
+function bodyHash(body: string): string {
+  return createHash('sha256').update(body, 'utf8').digest('hex');
+}
+
+function withHeader(packId: string, version: string, hash: string, body: string): string {
+  return [
+    '# Managed by sh1pt Actions Fleet',
+    `# pack: ${packId}@${version}`,
+    '# install: sh1pt-actions-store',
+    `# hash: sha256:${hash}`,
+    '',
+    body,
+  ].join('\n');
+}
+
+function makeRender(content: string, hash: string, destination = '.github/workflows/ci.yml'): RenderResult {
+  return {
+    packId: 'test-pack',
+    packVersion: '1.0.0',
+    files: [
+      {
+        source: 'ci.yml.hbs',
+        destination,
+        mergeStrategy: 'replace-managed',
+        content,
+        hash,
+      },
+    ],
+  };
+}
+
+// ---------- renderUnifiedDiff ----------
+
+describe('renderUnifiedDiff', () => {
+  it('returns empty string for identical content', () => {
+    const text = 'line1\nline2\n';
+    expect(renderUnifiedDiff(text, text, 'file.txt')).toBe('');
+  });
+
+  it('shows all lines as additions for a new file (null old content)', () => {
+    const diff = renderUnifiedDiff(null, 'line1\nline2\n', 'new.yml');
+    expect(diff).toContain('+line1');
+    expect(diff).toContain('+line2');
+    expect(diff).toContain('--- /dev/null');
+    expect(diff).toContain('+++ b/new.yml');
+    // No removal lines (lines starting with a single '-', not the '---' header)
+    const removalLines = diff.split('\n').filter((l) => /^-(?!-)/.test(l));
+    expect(removalLines).toHaveLength(0);
+  });
+
+  it('shows removed lines with - prefix', () => {
+    const diff = renderUnifiedDiff('old\n', 'new\n', 'file.txt');
+    expect(diff).toContain('-old');
+    expect(diff).toContain('+new');
+  });
+
+  it('includes @@ hunk header', () => {
+    const diff = renderUnifiedDiff('a\n', 'b\n', 'file.txt');
+    expect(diff).toContain('@@');
+  });
+
+  it('includes context lines around changes', () => {
+    const oldContent = ['ctx1', 'ctx2', 'ctx3', 'CHANGE', 'ctx4', 'ctx5', 'ctx6'].join('\n') + '\n';
+    const newContent = ['ctx1', 'ctx2', 'ctx3', 'CHANGED', 'ctx4', 'ctx5', 'ctx6'].join('\n') + '\n';
+    const diff = renderUnifiedDiff(oldContent, newContent, 'file.txt');
+    expect(diff).toContain(' ctx1');
+    expect(diff).toContain(' ctx6');
+    expect(diff).toContain('-CHANGE');
+    expect(diff).toContain('+CHANGED');
+  });
+
+  it('respects custom context line count', () => {
+    const oldContent = ['a', 'b', 'c', 'CHANGE', 'd', 'e', 'f'].join('\n') + '\n';
+    const newContent = ['a', 'b', 'c', 'CHANGED', 'd', 'e', 'f'].join('\n') + '\n';
+    const diff1 = renderUnifiedDiff(oldContent, newContent, 'file.txt', 1);
+    const diff3 = renderUnifiedDiff(oldContent, newContent, 'file.txt', 3);
+    // With 1 line of context, lines 'a' and 'b' should NOT appear as context lines
+    const contextLines1 = diff1.split('\n').filter((l) => /^ /.test(l));
+    expect(contextLines1.some((l) => l.trim() === 'a')).toBe(false);
+    // With 3 lines of context, 'a' should appear as a context line
+    const contextLines3 = diff3.split('\n').filter((l) => /^ /.test(l));
+    expect(contextLines3.some((l) => l.trim() === 'a')).toBe(true);
+  });
+});
+
+// ---------- renderPlanPreview ----------
+
+describe('renderPlanPreview', () => {
+  const body = 'name: CI\non: push\n';
+  const hash = bodyHash(body);
+  const newContent = withHeader('test-pack', '1.0.0', hash, body);
+
+  it('returns "(no changes)" when all files are unchanged', async () => {
+    const repoDir = await mkdtemp(join(tmpdir(), 'sh1pt-diff-preview-'));
+    try {
+      const plan = await planDiff({
+        repoDir,
+        render: makeRender(newContent, hash),
+        readExisting: async () => withHeader('test-pack', '1.0.0', hash, body),
+      });
+      const preview = renderPlanPreview(plan);
+      expect(preview.trim()).toBe('(no changes)');
+    } finally {
+      await rm(repoDir, { recursive: true, force: true });
+    }
+  });
+
+  it('shows additions for a new file', async () => {
+    const repoDir = await mkdtemp(join(tmpdir(), 'sh1pt-diff-preview-'));
+    try {
+      const plan = await planDiff({
+        repoDir,
+        render: makeRender(newContent, hash),
+        readExisting: async () => null,
+      });
+      const preview = renderPlanPreview(plan);
+      expect(preview).toContain('--- /dev/null');
+      expect(preview).toContain('+++ b/.github/workflows/ci.yml');
+      expect(preview).toContain('+name: CI');
+    } finally {
+      await rm(repoDir, { recursive: true, force: true });
+    }
+  });
+
+  it('shows a unified diff for an updated file', async () => {
+    const repoDir = await mkdtemp(join(tmpdir(), 'sh1pt-diff-preview-'));
+    try {
+      const oldBody = 'name: OLD\non: push\n';
+      const oldHash = bodyHash(oldBody);
+      const oldContent = withHeader('test-pack', '0.9.0', oldHash, oldBody);
+
+      const plan = await planDiff({
+        repoDir,
+        render: makeRender(newContent, hash),
+        readExisting: async () => oldContent,
+      });
+      const preview = renderPlanPreview(plan);
+      expect(preview).toContain('-name: OLD');
+      expect(preview).toContain('+name: CI');
+    } finally {
+      await rm(repoDir, { recursive: true, force: true });
+    }
+  });
+
+  it('shows a conflict warning for unmanaged files', async () => {
+    const repoDir = await mkdtemp(join(tmpdir(), 'sh1pt-diff-preview-'));
+    try {
+      const plan = await planDiff({
+        repoDir,
+        render: makeRender(newContent, hash),
+        readExisting: async () => 'name: existing\n',
+      });
+      const preview = renderPlanPreview(plan);
+      expect(preview).toContain('CONFLICT (unmanaged)');
+      expect(preview).toContain('--force');
+    } finally {
+      await rm(repoDir, { recursive: true, force: true });
+    }
+  });
+
+  it('shows a conflict warning for other-pack files', async () => {
+    const repoDir = await mkdtemp(join(tmpdir(), 'sh1pt-diff-preview-'));
+    try {
+      const otherBody = 'name: other\n';
+      const plan = await planDiff({
+        repoDir,
+        render: makeRender(newContent, hash),
+        readExisting: async () => withHeader('other-pack', '2.0.0', bodyHash(otherBody), otherBody),
+      });
+      const preview = renderPlanPreview(plan);
+      expect(preview).toContain('CONFLICT (other-pack)');
+      expect(preview).toContain('other-pack@2.0.0');
+    } finally {
+      await rm(repoDir, { recursive: true, force: true });
+    }
+  });
+});