get_git_diff

Instructions

Implementation Reference

• src/access/GitAccess.ts:137-179 (handler)

  Core implementation of getDiff that executes `git diff --stat` and `git diff` commands, parses additions/deletions, file list, and truncates output at 80,000 chars.

  async function getDiff(
    repoDir: string,
    base?: string,
    filePath?: string,
  ): Promise<DiffResult> {
    const MAX_DIFF = 80_000;
    const ref = base ?? 'HEAD~1';
  
    // Stat summary: additions/deletions + file list
    const statArgs = ['-C', repoDir, 'diff', '--stat', ref, 'HEAD'];
    if (filePath) statArgs.push('--', filePath);
  
    // Full diff
    const diffArgs = ['-C', repoDir, 'diff', ref, 'HEAD'];
    if (filePath) diffArgs.push('--', filePath);
  
    const [statResult, diffResult] = await Promise.all([
      execFileAsync('git', statArgs),
      execFileAsync('git', diffArgs),
    ]);
  
    const raw = diffResult.stdout;
    const truncated = raw.length > MAX_DIFF;
    const diff = truncated ? raw.slice(0, MAX_DIFF) + '\n\n[...truncated]' : raw;
  
    // Parse additions/deletions from stat
    const addMatch = statResult.stdout.match(/(\d+) insertion/);
    const delMatch = statResult.stdout.match(/(\d+) deletion/);
  
    // File list from stat lines
    const files = statResult.stdout
      .split('\n')
      .filter((l) => l.includes('|'))
      .map((l) => (l.split('|')[0] ?? '').trim());
  
    return {
      diff,
      files,
      additions: addMatch?.[1] != null ? parseInt(addMatch[1], 10) : 0,
      deletions: delMatch?.[1] != null ? parseInt(delMatch[1], 10) : 0,
      truncated,
    };
  }

• src/tools/dev-lifecycle.tool.ts:25-36 (schema)

  Zod schema for get_git_diff: optional 'base' (default HEAD~1) and 'file' (single file scope) params.

  export const GetGitDiffSchema = z.object({
    base: z
      .string()
      .optional()
      .describe(
        'Base git ref to diff against. Defaults to HEAD~1 (last commit). Use "HEAD" for uncommitted changes.',
      ),
    file: z
      .string()
      .optional()
      .describe('Optional file path to scope the diff to a single file.'),
  });

• src/tools/dev-lifecycle.tool.ts:66-77 (registration)

  MCP tool registration of 'get_git_diff' with schema and handler that delegates to manager.getDiff.

    server.tool(
      'get_git_diff',
      'Get the full unified diff between two refs (default: HEAD~1..HEAD). Returns diff text, file list, and addition/deletion counts. Use to review changes before logging them to the ledger.',
      GetGitDiffSchema.shape,
      async (args) => {
        const result = await manager.getDiff(args.base, args.file);
        return {
          content: [{ type: 'text' as const, text: JSON.stringify(result, null, 2) }],
        };
      },
    );
  }

• src/managers/DevLifecycleManager.ts:40-43 (helper)

  DevLifecycleManager interface declaring getDiff method.

  export interface DevLifecycleManager {
    runTypecheck(servicePath: string): Promise<TypecheckResult>;
    runTests(servicePath: string, pattern?: string): Promise<TestResult>;
    getDiff(base?: string, filePath?: string): Promise<DiffResult>;

• src/managers/DevLifecycleManager.ts:210-212 (helper)

  Manager getDiff method that delegates to GitAccess.getDiff with the repo directory.

  async function getDiff(base?: string, filePath?: string): Promise<DiffResult> {
    return git.getDiff(repoDir, base, filePath);
  }