Pseudo-JS code for creating a commit via the GitHub API from a Probot app

createCommit.js

// Getting tree
const { data: baseTree } = await client.gitdata.getTree({
  owner: login,
  repo: repo,
  tree_sha: sha,
  recursive: 1
})

const baseSha = baseTree.sha
const baseEntriesByPath = baseTree.tree.reduce((entriesByPath, entry) => {
  entriesByPath[entry.path] = entry
  return entriesByPath
}, {})

// For each file you want to update, create Blobs
const updatedFilePath = 'README.md'
const updatedFileContent = 'foobar'
const { data: blobData } = await client.gitdata.createBlob({
  owner: login,
  repo: repo,
  content: Buffer.from(updatedFileContent).toString('base64'),
  encoding: 'base64'
})

// etc. etc.

// Creating tree changeset
const treeChangeset = []
const fileMode = baseEntriesByPath[updateFilePath] ? baseEntriesByPath[updateFilePath].mode : '100644'
treeChangeset.push({ path: updateFilePath, sha: blobData.sha, mode: fileMode })

// Creating tree
const { data: newTreeData } = await client.gitdata.createTree({
  owner: login,
  repo: repo,
  tree: treeChangeset,
  base_tree: baseSha
})

// Turn that tree into a commit
// Ensure you use the user's client to make them the author here, if desired
// But definitely make the bot the committer
const userClient = getUserClientMagically()
const { data: commitData } = await userClient.gitdata.createCommit({
  owner: login,
  repo: repo,
  message: 'Automatic commit from MyAmazingProbotApp',
  parents: [baseSha],
  tree: newTreeData.sha || baseSha,
  committer: {
    name: 'MyAmazingProbotApp[bot]',
    email: 'MyAmazingProbotApp[bot]@users.noreply.github.com'
  }
})

// We've committed, update the HEAD
// Updating HEAD for the commit
await client.gitdata.updateRef({
  owner: login,
  repo: repo,
  ref: `heads/myPrBranchName`,
  sha: commitData.sha
})