index.js

const commentBody = `
Thanks for your submission.

It appears that you've created a pull request using one of our repository's branches. Since this is
almost always a mistake, we're going to go ahead and close this. If it was intentional, please
let us know what you were intending and we can see about reopening it.

Thanks again!
`

async function addInvalidLabel (context, issue) {
  const params = Object.assign({}, issue, {labels: ['invalid']})

  await ensureLabelExists(context, {name: 'invalid', color: 'e6e6e6'})
  await context.github.issues.addLabels(params)
}

async function close (context, params) {
  const closeParams = Object.assign({}, params, {state: 'closed'})

  return context.github.issues.edit(closeParams)
}

async function comment (context, params) {
  return context.github.issues.createComment(params)
}

async function ensureLabelExists (context, {name, color}) {
  return context.github.issues.getLabel(context.repo({name})).catch(() => {
    return context.github.issues.createLabel(context.repo({name, color}))
  })
}

async function hasPushAccess (context, params) {
  const permissionResponse = await context.github.repos.reviewUserPermissionLevel(params)
  const level = permissionResponse.data.permission

  return level === 'admin' || level === 'write'
}

module.exports = (robot) => {
  robot.on('pull_request.opened', async context => {
    const {owner} = context.repo()
    const branchLabel = context.payload.pull_request.head.label

    // If the branch label starts with the owner name, then it is a PR from a branch in the local
    // repo
    if (branchLabel.startsWith(owner)) {
      robot.log.debug(`PR created from branch in the local repo`)

      const username = context.payload.pull_request.user.login
      const canPush = await hasPushAccess(context, context.repo({username}))

      // If the user creating the PR from a local branch doesn't have push access, then they
      // can't push to their own PR and it isn't going to be useful
      if (!canPush) {
        robot.log.debug(`PR created from repo branch and user cannot push - closing PR`)

        await comment(context, context.issue({body: commentBody}))
        await addInvalidLabel(context, context.issue())

        return close(context, context.issue())
      }
    }
  })
}