next.js/packages/next/src/telemetry/project-id.ts

import { exec } from 'child_process'

// Q: Why does Next.js need a project ID? Why is it looking at my git remote?
// A:
// Next.js' telemetry is and always will be completely anonymous. Because of
// this, we need a way to differentiate different projects to track feature
// usage accurately. For example, to prevent a feature from appearing to be
// constantly `used` and then `unused` when switching between local projects.
// To reiterate,
// we **never** can read your actual git remote. The value is hashed one-way
// with random salt data, making it impossible for us to reverse or try to
// guess the remote by re-computing hashes.

async function _getProjectIdByGit() {
  try {
    let resolve: (value: Buffer | string) => void, reject: (err: Error) => void
    const promise = new Promise<Buffer | string>((res, rej) => {
      resolve = res
      reject = rej
    })

    exec(
      `git config --local --get remote.origin.url`,
      {
        timeout: 1000,
        windowsHide: true,
      },
      (error: null | Error, stdout: Buffer | string) => {
        if (error) {
          reject(error)
          return
        }
        resolve(stdout)
      }
    )

    return String(await promise).trim()
  } catch (_) {
    return null
  }
}

export async function getRawProjectId(): Promise<string> {
  return (
    (await _getProjectIdByGit()) || process.env.REPOSITORY_URL || process.cwd()
  )
}