Get Git diff

Instructions

Implementation Reference

• src/index.ts:32-84 (handler)

  The handler function for the 'git_diff' tool. It constructs git diff arguments based on the mode ('working', 'staged', 'range'), runs git diff and git diff --name-status using the runGit helper, processes the output to list changed files, truncates if necessary, and returns formatted content.

  async ({ mode = 'working', base, head, pathSpec, maxBytes = 200_000 }) => {
    let args: string[] = ['diff', '-U3']
  
    if (mode === 'staged') {
      args = ['diff', '--staged', '-U3']
    }
  
    if (mode === 'range' && (!base || !head)) {
      throw new Error('For mode=range informe base e head')
    }
  
    if (mode === 'range') {
      args = ['diff', `${base}...${head}`, '-U3']
    }
  
    if (pathSpec && pathSpec.length) {
      args.push('--', ...pathSpec)
    }
  
    const nameStatus = await runGit(
      mode === 'range'
        ? ['diff', '--name-status', `${base}...${head}`]
        : mode === 'staged'
        ? ['diff', '--staged', '--name-status']
        : ['diff', '--name-status']
    )
  
    const diff = await runGit(args)
    const truncated =
      diff.length > maxBytes
        ? diff.slice(0, maxBytes) + '\n\n[...truncated...]'
        : diff
  
    const files = nameStatus
      .split('\n')
      .filter(Boolean)
      .map((line) => {
        const [status, ...rest] = line.split(/\s+/)
        return { status, file: rest.join(' ') }
      })
  
    return {
      content: [
        {
          type: 'text',
          text: `Changed files:\n${files
            .map((f) => `${f.status}\t${f.file}`)
            .join('\n')}`,
        },
        { type: 'text', text: '\n--- DIFF START ---\n' + truncated },
      ],
    }
  }

• src/index.ts:19-30 (schema)

  Input schema for git_diff tool using Zod: mode (enum: working/staged/range), base/head (strings opt), pathSpec (array strings opt), maxBytes (number opt).

  inputSchema: {
    mode: z.enum(['working', 'staged', 'range']).default('working'),
    base: z.string().optional(),
    head: z.string().optional(),
    pathSpec: z.array(z.string()).optional(),
    maxBytes: z
      .number()
      .int()
      .positive()
      .max(5 * 1024 * 1024)
      .optional(),
  },

• src/index.ts:13-85 (registration)

  Registers the 'git_diff' tool with McpServer using server.registerTool, providing title, description, inputSchema, and the handler function.

  server.registerTool(
    'git_diff',
    {
      title: 'Get Git diff',
      description:
        'Retorna um diff do repositório atual. Use para entender alterações locais.',
      inputSchema: {
        mode: z.enum(['working', 'staged', 'range']).default('working'),
        base: z.string().optional(),
        head: z.string().optional(),
        pathSpec: z.array(z.string()).optional(),
        maxBytes: z
          .number()
          .int()
          .positive()
          .max(5 * 1024 * 1024)
          .optional(),
      },
    },
    async ({ mode = 'working', base, head, pathSpec, maxBytes = 200_000 }) => {
      let args: string[] = ['diff', '-U3']
  
      if (mode === 'staged') {
        args = ['diff', '--staged', '-U3']
      }
  
      if (mode === 'range' && (!base || !head)) {
        throw new Error('For mode=range informe base e head')
      }
  
      if (mode === 'range') {
        args = ['diff', `${base}...${head}`, '-U3']
      }
  
      if (pathSpec && pathSpec.length) {
        args.push('--', ...pathSpec)
      }
  
      const nameStatus = await runGit(
        mode === 'range'
          ? ['diff', '--name-status', `${base}...${head}`]
          : mode === 'staged'
          ? ['diff', '--staged', '--name-status']
          : ['diff', '--name-status']
      )
  
      const diff = await runGit(args)
      const truncated =
        diff.length > maxBytes
          ? diff.slice(0, maxBytes) + '\n\n[...truncated...]'
          : diff
  
      const files = nameStatus
        .split('\n')
        .filter(Boolean)
        .map((line) => {
          const [status, ...rest] = line.split(/\s+/)
          return { status, file: rest.join(' ') }
        })
  
      return {
        content: [
          {
            type: 'text',
            text: `Changed files:\n${files
              .map((f) => `${f.status}\t${f.file}`)
              .join('\n')}`,
          },
          { type: 'text', text: '\n--- DIFF START ---\n' + truncated },
        ],
      }
    }
  )

• src/helpers/github.ts:9-15 (helper)

  runGit helper function that promisifies execFile to run git commands with given args, returns trimmed stdout. Used by git_diff handler to execute git diff and git --name-status.

  export async function runGit(args: string[], cwd = process.cwd()) {
    const { stdout } = await pexec('git', ['--no-pager', ...args], {
      cwd,
      maxBuffer: 1024 * 1024 * 20,
    })
    return stdout.trim()
  }