Convert checkout to a regular action (#70)

8 files changed, 1161 insertions, 0 deletions

diff --git a/src/fs-helper.ts b/src/fs-helper.ts
new file mode 100644
index 0000000..c443404
--- /dev/null
+++ b/src/fs-helper.ts
@@ -0,0 +1,77 @@
+import * as fs from 'fs'
+
+export function directoryExistsSync(path: string, required?: boolean): boolean {
+  if (!path) {
+    throw new Error("Arg 'path' must not be empty")
+  }
+
+  let stats: fs.Stats
+  try {
+    stats = fs.statSync(path)
+  } catch (error) {
+    if (error.code === 'ENOENT') {
+      if (!required) {
+        return false
+      }
+
+      throw new Error(`Directory '${path}' does not exist`)
+    }
+
+    throw new Error(
+      `Encountered an error when checking whether path '${path}' exists: ${error.message}`
+    )
+  }
+
+  if (stats.isDirectory()) {
+    return true
+  } else if (!required) {
+    return false
+  }
+
+  throw new Error(`Directory '${path}' does not exist`)
+}
+
+export function existsSync(path: string): boolean {
+  if (!path) {
+    throw new Error("Arg 'path' must not be empty")
+  }
+
+  try {
+    fs.statSync(path)
+  } catch (error) {
+    if (error.code === 'ENOENT') {
+      return false
+    }
+
+    throw new Error(
+      `Encountered an error when checking whether path '${path}' exists: ${error.message}`
+    )
+  }
+
+  return true
+}
+
+export function fileExistsSync(path: string): boolean {
+  if (!path) {
+    throw new Error("Arg 'path' must not be empty")
+  }
+
+  let stats: fs.Stats
+  try {
+    stats = fs.statSync(path)
+  } catch (error) {
+    if (error.code === 'ENOENT') {
+      return false
+    }
+
+    throw new Error(
+      `Encountered an error when checking whether path '${path}' exists: ${error.message}`
+    )
+  }
+
+  if (!stats.isDirectory()) {
+    return true
+  }
+
+  return false
+}
diff --git a/src/git-command-manager.ts b/src/git-command-manager.ts
new file mode 100644
index 0000000..6e4f22f
--- /dev/null
+++ b/src/git-command-manager.ts
@@ -0,0 +1,399 @@
+import * as core from '@actions/core'
+import * as exec from '@actions/exec'
+import * as fshelper from './fs-helper'
+import * as io from '@actions/io'
+import * as path from 'path'
+import {GitVersion} from './git-version'
+
+export interface IGitCommandManager {
+  branchDelete(remote: boolean, branch: string): Promise<void>
+  branchExists(remote: boolean, pattern: string): Promise<boolean>
+  branchList(remote: boolean): Promise<string[]>
+  checkout(ref: string, startPoint: string): Promise<void>
+  checkoutDetach(): Promise<void>
+  config(configKey: string, configValue: string): Promise<void>
+  configExists(configKey: string): Promise<boolean>
+  fetch(fetchDepth: number, refSpec: string[]): Promise<void>
+  getWorkingDirectory(): string
+  init(): Promise<void>
+  isDetached(): Promise<boolean>
+  lfsFetch(ref: string): Promise<void>
+  lfsInstall(): Promise<void>
+  log1(): Promise<void>
+  remoteAdd(remoteName: string, remoteUrl: string): Promise<void>
+  tagExists(pattern: string): Promise<boolean>
+  tryClean(): Promise<boolean>
+  tryConfigUnset(configKey: string): Promise<boolean>
+  tryDisableAutomaticGarbageCollection(): Promise<boolean>
+  tryGetFetchUrl(): Promise<string>
+  tryReset(): Promise<boolean>
+}
+
+export async function CreateCommandManager(
+  workingDirectory: string,
+  lfs: boolean
+): Promise<IGitCommandManager> {
+  return await GitCommandManager.createCommandManager(workingDirectory, lfs)
+}
+
+class GitCommandManager {
+  private gitEnv = {
+    GIT_TERMINAL_PROMPT: '0', // Disable git prompt
+    GCM_INTERACTIVE: 'Never' // Disable prompting for git credential manager
+  }
+  private gitPath = ''
+  private lfs = false
+  private workingDirectory = ''
+
+  // Private constructor; use createCommandManager()
+  private constructor() {}
+
+  async branchDelete(remote: boolean, branch: string): Promise<void> {
+    const args = ['branch', '--delete', '--force']
+    if (remote) {
+      args.push('--remote')
+    }
+    args.push(branch)
+
+    await this.execGit(args)
+  }
+
+  async branchExists(remote: boolean, pattern: string): Promise<boolean> {
+    const args = ['branch', '--list']
+    if (remote) {
+      args.push('--remote')
+    }
+    args.push(pattern)
+
+    const output = await this.execGit(args)
+    return !!output.stdout.trim()
+  }
+
+  async branchList(remote: boolean): Promise<string[]> {
+    const result: string[] = []
+
+    // Note, this implementation uses "rev-parse --symbolic" because the output from
+    // "branch --list" is more difficult when in a detached HEAD state.
+
+    const args = ['rev-parse', '--symbolic']
+    if (remote) {
+      args.push('--remotes=origin')
+    } else {
+      args.push('--branches')
+    }
+
+    const output = await this.execGit(args)
+
+    for (let branch of output.stdout.trim().split('\n')) {
+      branch = branch.trim()
+      if (branch) {
+        result.push(branch)
+      }
+    }
+
+    return result
+  }
+
+  async checkout(ref: string, startPoint: string): Promise<void> {
+    const args = ['checkout', '--progress', '--force']
+    if (startPoint) {
+      args.push('-B', ref, startPoint)
+    } else {
+      args.push(ref)
+    }
+
+    await this.execGit(args)
+  }
+
+  async checkoutDetach(): Promise<void> {
+    const args = ['checkout', '--detach']
+    await this.execGit(args)
+  }
+
+  async config(configKey: string, configValue: string): Promise<void> {
+    await this.execGit(['config', configKey, configValue])
+  }
+
+  async configExists(configKey: string): Promise<boolean> {
+    const pattern = configKey.replace(/[^a-zA-Z0-9_]/g, x => {
+      return `\\${x}`
+    })
+    const output = await this.execGit(
+      ['config', '--name-only', '--get-regexp', pattern],
+      true
+    )
+    return output.exitCode === 0
+  }
+
+  async fetch(fetchDepth: number, refSpec: string[]): Promise<void> {
+    const args = [
+      '-c',
+      'protocol.version=2',
+      'fetch',
+      '--no-tags',
+      '--prune',
+      '--progress',
+      '--no-recurse-submodules'
+    ]
+    if (fetchDepth > 0) {
+      args.push(`--depth=${fetchDepth}`)
+    } else if (
+      fshelper.fileExistsSync(
+        path.join(this.workingDirectory, '.git', 'shallow')
+      )
+    ) {
+      args.push('--unshallow')
+    }
+
+    args.push('origin')
+    for (const arg of refSpec) {
+      args.push(arg)
+    }
+
+    let attempt = 1
+    const maxAttempts = 3
+    while (attempt <= maxAttempts) {
+      const allowAllExitCodes = attempt < maxAttempts
+      const output = await this.execGit(args, allowAllExitCodes)
+      if (output.exitCode === 0) {
+        break
+      }
+
+      const seconds = this.getRandomIntInclusive(1, 10)
+      core.warning(
+        `Git fetch failed with exit code ${output.exitCode}. Waiting ${seconds} seconds before trying again.`
+      )
+      await this.sleep(seconds * 1000)
+      attempt++
+    }
+  }
+
+  getWorkingDirectory(): string {
+    return this.workingDirectory
+  }
+
+  async init(): Promise<void> {
+    await this.execGit(['init', this.workingDirectory])
+  }
+
+  async isDetached(): Promise<boolean> {
+    // Note, this implementation uses "branch --show-current" because
+    // "rev-parse --symbolic-full-name HEAD" can fail on a new repo
+    // with nothing checked out.
+
+    const output = await this.execGit(['branch', '--show-current'])
+    return output.stdout.trim() === ''
+  }
+
+  async lfsFetch(ref: string): Promise<void> {
+    const args = ['lfs', 'fetch', 'origin', ref]
+
+    let attempt = 1
+    const maxAttempts = 3
+    while (attempt <= maxAttempts) {
+      const allowAllExitCodes = attempt < maxAttempts
+      const output = await this.execGit(args, allowAllExitCodes)
+      if (output.exitCode === 0) {
+        break
+      }
+
+      const seconds = this.getRandomIntInclusive(1, 10)
+      core.warning(
+        `Git lfs fetch failed with exit code ${output.exitCode}. Waiting ${seconds} seconds before trying again.`
+      )
+      await this.sleep(seconds * 1000)
+      attempt++
+    }
+  }
+
+  async lfsInstall(): Promise<void> {
+    await this.execGit(['lfs', 'install', '--local'])
+  }
+
+  async log1(): Promise<void> {
+    await this.execGit(['log', '-1'])
+  }
+
+  async remoteAdd(remoteName: string, remoteUrl: string): Promise<void> {
+    await this.execGit(['remote', 'add', remoteName, remoteUrl])
+  }
+
+  async tagExists(pattern: string): Promise<boolean> {
+    const output = await this.execGit(['tag', '--list', pattern])
+    return !!output.stdout.trim()
+  }
+
+  async tryClean(): Promise<boolean> {
+    const output = await this.execGit(['clean', '-ffdx'], true)
+    return output.exitCode === 0
+  }
+
+  async tryConfigUnset(configKey: string): Promise<boolean> {
+    const output = await this.execGit(
+      ['config', '--unset-all', configKey],
+      true
+    )
+    return output.exitCode === 0
+  }
+
+  async tryDisableAutomaticGarbageCollection(): Promise<boolean> {
+    const output = await this.execGit(['config', 'gc.auto', '0'], true)
+    return output.exitCode === 0
+  }
+
+  async tryGetFetchUrl(): Promise<string> {
+    const output = await this.execGit(
+      ['config', '--get', 'remote.origin.url'],
+      true
+    )
+
+    if (output.exitCode !== 0) {
+      return ''
+    }
+
+    const stdout = output.stdout.trim()
+    if (stdout.includes('\n')) {
+      return ''
+    }
+
+    return stdout
+  }
+
+  async tryReset(): Promise<boolean> {
+    const output = await this.execGit(['reset', '--hard', 'HEAD'], true)
+    return output.exitCode === 0
+  }
+
+  static async createCommandManager(
+    workingDirectory: string,
+    lfs: boolean
+  ): Promise<GitCommandManager> {
+    const result = new GitCommandManager()
+    await result.initializeCommandManager(workingDirectory, lfs)
+    return result
+  }
+
+  private async execGit(
+    args: string[],
+    allowAllExitCodes = false
+  ): Promise<GitOutput> {
+    fshelper.directoryExistsSync(this.workingDirectory, true)
+
+    const result = new GitOutput()
+
+    const env = {}
+    for (const key of Object.keys(process.env)) {
+      env[key] = process.env[key]
+    }
+    for (const key of Object.keys(this.gitEnv)) {
+      env[key] = this.gitEnv[key]
+    }
+
+    const stdout: string[] = []
+
+    const options = {
+      cwd: this.workingDirectory,
+      env,
+      ignoreReturnCode: allowAllExitCodes,
+      listeners: {
+        stdout: (data: Buffer) => {
+          stdout.push(data.toString())
+        }
+      }
+    }
+
+    result.exitCode = await exec.exec(`"${this.gitPath}"`, args, options)
+    result.stdout = stdout.join('')
+    return result
+  }
+
+  private async initializeCommandManager(
+    workingDirectory: string,
+    lfs: boolean
+  ): Promise<void> {
+    this.workingDirectory = workingDirectory
+
+    // Git-lfs will try to pull down assets if any of the local/user/system setting exist.
+    // If the user didn't enable `LFS` in their pipeline definition, disable LFS fetch/checkout.
+    this.lfs = lfs
+    if (!this.lfs) {
+      this.gitEnv['GIT_LFS_SKIP_SMUDGE'] = '1'
+    }
+
+    this.gitPath = await io.which('git', true)
+
+    // Git version
+    core.debug('Getting git version')
+    let gitVersion = new GitVersion()
+    let gitOutput = await this.execGit(['version'])
+    let stdout = gitOutput.stdout.trim()
+    if (!stdout.includes('\n')) {
+      const match = stdout.match(/\d+\.\d+(\.\d+)?/)
+      if (match) {
+        gitVersion = new GitVersion(match[0])
+      }
+    }
+    if (!gitVersion.isValid()) {
+      throw new Error('Unable to determine git version')
+    }
+
+    // Minimum git version
+    // Note:
+    // - Auth header not supported before 2.9
+    // - Wire protocol v2 not supported before 2.18
+    const minimumGitVersion = new GitVersion('2.18')
+    if (!gitVersion.checkMinimum(minimumGitVersion)) {
+      throw new Error(
+        `Minimum required git version is ${minimumGitVersion}. Your git ('${this.gitPath}') is ${gitVersion}`
+      )
+    }
+
+    if (this.lfs) {
+      // Git-lfs version
+      core.debug('Getting git-lfs version')
+      let gitLfsVersion = new GitVersion()
+      const gitLfsPath = await io.which('git-lfs', true)
+      gitOutput = await this.execGit(['lfs', 'version'])
+      stdout = gitOutput.stdout.trim()
+      if (!stdout.includes('\n')) {
+        const match = stdout.match(/\d+\.\d+(\.\d+)?/)
+        if (match) {
+          gitLfsVersion = new GitVersion(match[0])
+        }
+      }
+      if (!gitLfsVersion.isValid()) {
+        throw new Error('Unable to determine git-lfs version')
+      }
+
+      // Minimum git-lfs version
+      // Note:
+      // - Auth header not supported before 2.1
+      const minimumGitLfsVersion = new GitVersion('2.1')
+      if (!gitLfsVersion.checkMinimum(minimumGitLfsVersion)) {
+        throw new Error(
+          `Minimum required git-lfs version is ${minimumGitLfsVersion}. Your git-lfs ('${gitLfsPath}') is ${gitLfsVersion}`
+        )
+      }
+    }
+
+    // Set the user agent
+    const gitHttpUserAgent = `git/${gitVersion} (github-actions-checkout)`
+    core.debug(`Set git useragent to: ${gitHttpUserAgent}`)
+    this.gitEnv['GIT_HTTP_USER_AGENT'] = gitHttpUserAgent
+  }
+
+  private getRandomIntInclusive(minimum: number, maximum: number): number {
+    minimum = Math.floor(minimum)
+    maximum = Math.floor(maximum)
+    return Math.floor(Math.random() * (maximum - minimum + 1)) + minimum
+  }
+
+  private async sleep(milliseconds): Promise<void> {
+    return new Promise(resolve => setTimeout(resolve, milliseconds))
+  }
+}
+
+class GitOutput {
+  stdout = ''
+  exitCode = 0
+}
diff --git a/src/git-source-provider.ts b/src/git-source-provider.ts
new file mode 100644
index 0000000..0752100
--- /dev/null
+++ b/src/git-source-provider.ts
@@ -0,0 +1,246 @@
+import * as core from '@actions/core'
+import * as coreCommand from '@actions/core/lib/command'
+import * as fs from 'fs'
+import * as fsHelper from './fs-helper'
+import * as gitCommandManager from './git-command-manager'
+import * as io from '@actions/io'
+import * as path from 'path'
+import * as refHelper from './ref-helper'
+import {IGitCommandManager} from './git-command-manager'
+
+const authConfigKey = `http.https://github.com/.extraheader`
+
+export interface ISourceSettings {
+  repositoryPath: string
+  repositoryOwner: string
+  repositoryName: string
+  ref: string
+  commit: string
+  clean: boolean
+  fetchDepth: number
+  lfs: boolean
+  accessToken: string
+}
+
+export async function getSource(settings: ISourceSettings): Promise<void> {
+  core.info(
+    `Syncing repository: ${settings.repositoryOwner}/${settings.repositoryName}`
+  )
+  const repositoryUrl = `https://github.com/${encodeURIComponent(
+    settings.repositoryOwner
+  )}/${encodeURIComponent(settings.repositoryName)}`
+
+  // Remove conflicting file path
+  if (fsHelper.fileExistsSync(settings.repositoryPath)) {
+    await io.rmRF(settings.repositoryPath)
+  }
+
+  // Create directory
+  let isExisting = true
+  if (!fsHelper.directoryExistsSync(settings.repositoryPath)) {
+    isExisting = false
+    await io.mkdirP(settings.repositoryPath)
+  }
+
+  // Git command manager
+  core.info(`Working directory is '${settings.repositoryPath}'`)
+  const git = await gitCommandManager.CreateCommandManager(
+    settings.repositoryPath,
+    settings.lfs
+  )
+
+  // Try prepare existing directory, otherwise recreate
+  if (
+    isExisting &&
+    !(await tryPrepareExistingDirectory(
+      git,
+      settings.repositoryPath,
+      repositoryUrl,
+      settings.clean
+    ))
+  ) {
+    await io.rmRF(settings.repositoryPath)
+    await io.mkdirP(settings.repositoryPath)
+  }
+
+  // Initialize the repository
+  if (
+    !fsHelper.directoryExistsSync(path.join(settings.repositoryPath, '.git'))
+  ) {
+    await git.init()
+    await git.remoteAdd('origin', repositoryUrl)
+  }
+
+  // Disable automatic garbage collection
+  if (!(await git.tryDisableAutomaticGarbageCollection())) {
+    core.warning(
+      `Unable to turn off git automatic garbage collection. The git fetch operation may trigger garbage collection and cause a delay.`
+    )
+  }
+
+  // Remove possible previous extraheader
+  await removeGitConfig(git, authConfigKey)
+
+  // Add extraheader (auth)
+  const base64Credentials = Buffer.from(
+    `x-access-token:${settings.accessToken}`,
+    'utf8'
+  ).toString('base64')
+  core.setSecret(base64Credentials)
+  const authConfigValue = `AUTHORIZATION: basic ${base64Credentials}`
+  await git.config(authConfigKey, authConfigValue)
+
+  // LFS install
+  if (settings.lfs) {
+    await git.lfsInstall()
+  }
+
+  // Fetch
+  const refSpec = refHelper.getRefSpec(settings.ref, settings.commit)
+  await git.fetch(settings.fetchDepth, refSpec)
+
+  // Checkout info
+  const checkoutInfo = await refHelper.getCheckoutInfo(
+    git,
+    settings.ref,
+    settings.commit
+  )
+
+  // LFS fetch
+  // Explicit lfs-fetch to avoid slow checkout (fetches one lfs object at a time).
+  // Explicit lfs fetch will fetch lfs objects in parallel.
+  if (settings.lfs) {
+    await git.lfsFetch(checkoutInfo.startPoint || checkoutInfo.ref)
+  }
+
+  // Checkout
+  await git.checkout(checkoutInfo.ref, checkoutInfo.startPoint)
+
+  // Dump some info about the checked out commit
+  await git.log1()
+
+  // Set intra-task state for cleanup
+  coreCommand.issueCommand(
+    'save-state',
+    {name: 'repositoryPath'},
+    settings.repositoryPath
+  )
+}
+
+export async function cleanup(repositoryPath: string): Promise<void> {
+  // Repo exists?
+  if (!fsHelper.fileExistsSync(path.join(repositoryPath, '.git', 'config'))) {
+    return
+  }
+  fsHelper.directoryExistsSync(repositoryPath, true)
+
+  // Remove the config key
+  const git = await gitCommandManager.CreateCommandManager(
+    repositoryPath,
+    false
+  )
+  await removeGitConfig(git, authConfigKey)
+}
+
+async function tryPrepareExistingDirectory(
+  git: IGitCommandManager,
+  repositoryPath: string,
+  repositoryUrl: string,
+  clean: boolean
+): Promise<boolean> {
+  // Fetch URL does not match
+  if (
+    !fsHelper.directoryExistsSync(path.join(repositoryPath, '.git')) ||
+    repositoryUrl !== (await git.tryGetFetchUrl())
+  ) {
+    return false
+  }
+
+  // Delete any index.lock and shallow.lock left by a previously canceled run or crashed git process
+  const lockPaths = [
+    path.join(repositoryPath, '.git', 'index.lock'),
+    path.join(repositoryPath, '.git', 'shallow.lock')
+  ]
+  for (const lockPath of lockPaths) {
+    try {
+      await io.rmRF(lockPath)
+    } catch (error) {
+      core.debug(`Unable to delete '${lockPath}'. ${error.message}`)
+    }
+  }
+
+  try {
+    // Checkout detached HEAD
+    if (!(await git.isDetached())) {
+      await git.checkoutDetach()
+    }
+
+    // Remove all refs/heads/*
+    let branches = await git.branchList(false)
+    for (const branch of branches) {
+      await git.branchDelete(false, branch)
+    }
+
+    // Remove all refs/remotes/origin/* to avoid conflicts
+    branches = await git.branchList(true)
+    for (const branch of branches) {
+      await git.branchDelete(true, branch)
+    }
+  } catch (error) {
+    core.warning(
+      `Unable to prepare the existing repository. The repository will be recreated instead.`
+    )
+    return false
+  }
+
+  // Clean
+  if (clean) {
+    let succeeded = true
+    if (!(await git.tryClean())) {
+      core.debug(
+        `The clean command failed. This might be caused by: 1) path too long, 2) permission issue, or 3) file in use. For futher investigation, manually run 'git clean -ffdx' on the directory '${repositoryPath}'.`
+      )
+      succeeded = false
+    } else if (!(await git.tryReset())) {
+      succeeded = false
+    }
+
+    if (!succeeded) {
+      core.warning(
+        `Unable to clean or reset the repository. The repository will be recreated instead.`
+      )
+    }
+
+    return succeeded
+  }
+
+  return true
+}
+
+async function removeGitConfig(
+  git: IGitCommandManager,
+  configKey: string
+): Promise<void> {
+  if (
+    (await git.configExists(configKey)) &&
+    !(await git.tryConfigUnset(configKey))
+  ) {
+    // Load the config contents
+    core.warning(
+      `Failed to remove '${configKey}' from the git config. Attempting to remove the config value by editing the file directly.`
+    )
+    const configPath = path.join(git.getWorkingDirectory(), '.git', 'config')
+    fsHelper.fileExistsSync(configPath)
+    let contents = fs.readFileSync(configPath).toString() || ''
+
+    // Filter - only includes lines that do not contain the config key
+    const upperConfigKey = configKey.toUpperCase()
+    const split = contents
+      .split('\n')
+      .filter(x => !x.toUpperCase().includes(upperConfigKey))
+    contents = split.join('\n')
+
+    // Rewrite the config file
+    fs.writeFileSync(configPath, contents)
+  }
+}
diff --git a/src/git-version.ts b/src/git-version.ts
new file mode 100644
index 0000000..44bee1a
--- /dev/null
+++ b/src/git-version.ts
@@ -0,0 +1,77 @@
+export class GitVersion {
+  private readonly major: number = NaN
+  private readonly minor: number = NaN
+  private readonly patch: number = NaN
+
+  /**
+   * Used for comparing the version of git and git-lfs against the minimum required version
+   * @param version the version string, e.g. 1.2 or 1.2.3
+   */
+  constructor(version?: string) {
+    if (version) {
+      const match = version.match(/^(\d+)\.(\d+)(\.(\d+))?$/)
+      if (match) {
+        this.major = Number(match[1])
+        this.minor = Number(match[2])
+        if (match[4]) {
+          this.patch = Number(match[4])
+        }
+      }
+    }
+  }
+
+  /**
+   * Compares the instance against a minimum required version
+   * @param minimum Minimum version
+   */
+  checkMinimum(minimum: GitVersion): boolean {
+    if (!minimum.isValid()) {
+      throw new Error('Arg minimum is not a valid version')
+    }
+
+    // Major is insufficient
+    if (this.major < minimum.major) {
+      return false
+    }
+
+    // Major is equal
+    if (this.major === minimum.major) {
+      // Minor is insufficient
+      if (this.minor < minimum.minor) {
+        return false
+      }
+
+      // Minor is equal
+      if (this.minor === minimum.minor) {
+        // Patch is insufficient
+        if (this.patch && this.patch < (minimum.patch || 0)) {
+          return false
+        }
+      }
+    }
+
+    return true
+  }
+
+  /**
+   * Indicates whether the instance was constructed from a valid version string
+   */
+  isValid(): boolean {
+    return !isNaN(this.major)
+  }
+
+  /**
+   * Returns the version as a string, e.g. 1.2 or 1.2.3
+   */
+  toString(): string {
+    let result = ''
+    if (this.isValid()) {
+      result = `${this.major}.${this.minor}`
+      if (!isNaN(this.patch)) {
+        result += `.${this.patch}`
+      }
+    }
+
+    return result
+  }
+}
diff --git a/src/input-helper.ts b/src/input-helper.ts
new file mode 100644
index 0000000..d7d8779
--- /dev/null
+++ b/src/input-helper.ts
@@ -0,0 +1,104 @@
+import * as core from '@actions/core'
+import * as fsHelper from './fs-helper'
+import * as github from '@actions/github'
+import * as path from 'path'
+import {ISourceSettings} from './git-source-provider'
+
+export function getInputs(): ISourceSettings {
+  const result = ({} as unknown) as ISourceSettings
+
+  // GitHub workspace
+  let githubWorkspacePath = process.env['GITHUB_WORKSPACE']
+  if (!githubWorkspacePath) {
+    throw new Error('GITHUB_WORKSPACE not defined')
+  }
+  githubWorkspacePath = path.resolve(githubWorkspacePath)
+  core.debug(`GITHUB_WORKSPACE = '${githubWorkspacePath}'`)
+  fsHelper.directoryExistsSync(githubWorkspacePath, true)
+
+  // Qualified repository
+  const qualifiedRepository =
+    core.getInput('repository') ||
+    `${github.context.repo.owner}/${github.context.repo.repo}`
+  core.debug(`qualified repository = '${qualifiedRepository}'`)
+  const splitRepository = qualifiedRepository.split('/')
+  if (
+    splitRepository.length !== 2 ||
+    !splitRepository[0] ||
+    !splitRepository[1]
+  ) {
+    throw new Error(
+      `Invalid repository '${qualifiedRepository}'. Expected format {owner}/{repo}.`
+    )
+  }
+  result.repositoryOwner = splitRepository[0]
+  result.repositoryName = splitRepository[1]
+
+  // Repository path
+  result.repositoryPath = core.getInput('path') || '.'
+  result.repositoryPath = path.resolve(
+    githubWorkspacePath,
+    result.repositoryPath
+  )
+  if (
+    !(result.repositoryPath + path.sep).startsWith(
+      githubWorkspacePath + path.sep
+    )
+  ) {
+    throw new Error(
+      `Repository path '${result.repositoryPath}' is not under '${githubWorkspacePath}'`
+    )
+  }
+
+  // Workflow repository?
+  const isWorkflowRepository =
+    qualifiedRepository.toUpperCase() ===
+    `${github.context.repo.owner}/${github.context.repo.repo}`.toUpperCase()
+
+  // Source branch, source version
+  result.ref = core.getInput('ref')
+  if (!result.ref) {
+    if (isWorkflowRepository) {
+      result.ref = github.context.ref
+      result.commit = github.context.sha
+    }
+
+    if (!result.ref && !result.commit) {
+      result.ref = 'refs/heads/master'
+    }
+  }
+  // SHA?
+  else if (result.ref.match(/^[0-9a-fA-F]{40}$/)) {
+    result.commit = result.ref
+    result.ref = ''
+  }
+  core.debug(`ref = '${result.ref}'`)
+  core.debug(`commit = '${result.commit}'`)
+
+  // Clean
+  result.clean = (core.getInput('clean') || 'true').toUpperCase() === 'TRUE'
+  core.debug(`clean = ${result.clean}`)
+
+  // Submodules
+  if (core.getInput('submodules')) {
+    throw new Error(
+      "The input 'submodules' is not supported in actions/checkout@v2"
+    )
+  }
+
+  // Fetch depth
+  result.fetchDepth = Math.floor(Number(core.getInput('fetch-depth') || '1'))
+  if (isNaN(result.fetchDepth) || result.fetchDepth < 0) {
+    result.fetchDepth = 0
+  }
+  core.debug(`fetch depth = ${result.fetchDepth}`)
+
+  // LFS
+  result.lfs = (core.getInput('lfs') || 'false').toUpperCase() === 'TRUE'
+  core.debug(`lfs = ${result.lfs}`)
+
+  // Access token
+  result.accessToken = core.getInput('token')
+
+  return result
+}
diff --git a/src/main.ts b/src/main.ts
new file mode 100644
index 0000000..26da3aa
--- /dev/null
+++ b/src/main.ts
@@ -0,0 +1,47 @@
+import * as core from '@actions/core'
+import * as coreCommand from '@actions/core/lib/command'
+import * as gitSourceProvider from './git-source-provider'
+import * as inputHelper from './input-helper'
+import * as path from 'path'
+
+const cleanupRepositoryPath = process.env['STATE_repositoryPath'] as string
+
+async function run(): Promise<void> {
+  try {
+    const sourceSettings = inputHelper.getInputs()
+
+    try {
+      // Register problem matcher
+      coreCommand.issueCommand(
+        'add-matcher',
+        {},
+        path.join(__dirname, 'problem-matcher.json')
+      )
+
+      // Get sources
+      await gitSourceProvider.getSource(sourceSettings)
+    } finally {
+      // Unregister problem matcher
+      coreCommand.issueCommand('remove-matcher', {owner: 'checkout-git'}, '')
+    }
+  } catch (error) {
+    core.setFailed(error.message)
+  }
+}
+
+async function cleanup(): Promise<void> {
+  try {
+    await gitSourceProvider.cleanup(cleanupRepositoryPath)
+  } catch (error) {
+    core.warning(error.message)
+  }
+}
+
+// Main
+if (!cleanupRepositoryPath) {
+  run()
+}
+// Post
+else {
+  cleanup()
+}
diff --git a/src/misc/generate-docs.ts b/src/misc/generate-docs.ts
new file mode 100644
index 0000000..c882c55
--- /dev/null
+++ b/src/misc/generate-docs.ts
@@ -0,0 +1,102 @@
+import * as fs from 'fs'
+import * as os from 'os'
+import * as path from 'path'
+import * as yaml from 'js-yaml'
+
+//
+// SUMMARY
+//
+// This script rebuilds the usage section in the README.md to be consistent with the action.yml
+
+function updateUsage(
+  actionReference: string,
+  actionYamlPath: string = 'action.yml',
+  readmePath: string = 'README.md',
+  startToken: string = '<!-- start usage -->',
+  endToken: string = '<!-- end usage -->'
+): void {
+  if (!actionReference) {
+    throw new Error('Parameter actionReference must not be empty')
+  }
+
+  // Load the action.yml
+  const actionYaml = yaml.safeLoad(fs.readFileSync(actionYamlPath).toString())
+
+  // Load the README
+  const originalReadme = fs.readFileSync(readmePath).toString()
+
+  // Find the start token
+  const startTokenIndex = originalReadme.indexOf(startToken)
+  if (startTokenIndex < 0) {
+    throw new Error(`Start token '${startToken}' not found`)
+  }
+
+  // Find the end token
+  const endTokenIndex = originalReadme.indexOf(endToken)
+  if (endTokenIndex < 0) {
+    throw new Error(`End token '${endToken}' not found`)
+  } else if (endTokenIndex < startTokenIndex) {
+    throw new Error('Start token must appear before end token')
+  }
+
+  // Build the new README
+  const newReadme: string[] = []
+
+  // Append the beginning
+  newReadme.push(originalReadme.substr(0, startTokenIndex + startToken.length))
+
+  // Build the new usage section
+  newReadme.push('```yaml', `- uses: ${actionReference}`, '  with:')
+  const inputs = actionYaml.inputs
+  let firstInput = true
+  for (const key of Object.keys(inputs)) {
+    const input = inputs[key]
+
+    // Line break between inputs
+    if (!firstInput) {
+      newReadme.push('')
+    }
+
+    // Constrain the width of the description
+    const width = 80
+    let description = input.description as string
+    while (description) {
+      // Longer than width? Find a space to break apart
+      let segment: string = description
+      if (description.length > width) {
+        segment = description.substr(0, width + 1)
+        while (!segment.endsWith(' ')) {
+          segment = segment.substr(0, segment.length - 1)
+        }
+      } else {
+        segment = description
+      }
+
+      description = description.substr(segment.length) // Remaining
+      segment = segment.trimRight() // Trim the trailing space
+      newReadme.push(`    # ${segment}`)
+    }
+
+    // Input and default
+    if (input.default !== undefined) {
+      newReadme.push(`    # Default: ${input.default}`)
+    }
+    newReadme.push(`    ${key}: ''`)
+
+    firstInput = false
+  }
+
+  newReadme.push('```')
+
+  // Append the end
+  newReadme.push(originalReadme.substr(endTokenIndex))
+
+  // Write the new README
+  fs.writeFileSync(readmePath, newReadme.join(os.EOL))
+}
+
+updateUsage(
+  'actions/checkout@preview',
+  path.join(__dirname, '..', '..', 'action.yml'),
+  path.join(__dirname, '..', '..', 'README.md')
+)
diff --git a/src/ref-helper.ts b/src/ref-helper.ts
new file mode 100644
index 0000000..ff256af
--- /dev/null
+++ b/src/ref-helper.ts
@@ -0,0 +1,109 @@
+import {IGitCommandManager} from './git-command-manager'
+
+export interface ICheckoutInfo {
+  ref: string
+  startPoint: string
+}
+
+export async function getCheckoutInfo(
+  git: IGitCommandManager,
+  ref: string,
+  commit: string
+): Promise<ICheckoutInfo> {
+  if (!git) {
+    throw new Error('Arg git cannot be empty')
+  }
+
+  if (!ref && !commit) {
+    throw new Error('Args ref and commit cannot both be empty')
+  }
+
+  const result = ({} as unknown) as ICheckoutInfo
+  const upperRef = (ref || '').toUpperCase()
+
+  // SHA only
+  if (!ref) {
+    result.ref = commit
+  }
+  // refs/heads/
+  else if (upperRef.startsWith('REFS/HEADS/')) {
+    const branch = ref.substring('refs/heads/'.length)
+    result.ref = branch
+    result.startPoint = `refs/remotes/origin/${branch}`
+  }
+  // refs/pull/
+  else if (upperRef.startsWith('REFS/PULL/')) {
+    const branch = ref.substring('refs/pull/'.length)
+    result.ref = `refs/remotes/pull/${branch}`
+  }
+  // refs/tags/
+  else if (upperRef.startsWith('REFS/')) {
+    result.ref = ref
+  }
+  // Unqualified ref, check for a matching branch or tag
+  else {
+    if (await git.branchExists(true, `origin/${ref}`)) {
+      result.ref = ref
+      result.startPoint = `refs/remotes/origin/${ref}`
+    } else if (await git.tagExists(`${ref}`)) {
+      result.ref = `refs/tags/${ref}`
+    } else {
+      throw new Error(
+        `A branch or tag with the name '${ref}' could not be found`
+      )
+    }
+  }
+
+  return result
+}
+
+export function getRefSpec(ref: string, commit: string): string[] {
+  if (!ref && !commit) {
+    throw new Error('Args ref and commit cannot both be empty')
+  }
+
+  const upperRef = (ref || '').toUpperCase()
+
+  // SHA
+  if (commit) {
+    // refs/heads
+    if (upperRef.startsWith('REFS/HEADS/')) {
+      const branch = ref.substring('refs/heads/'.length)
+      return [`+${commit}:refs/remotes/origin/${branch}`]
+    }
+    // refs/pull/
+    else if (upperRef.startsWith('REFS/PULL/')) {
+      const branch = ref.substring('refs/pull/'.length)
+      return [`+${commit}:refs/remotes/pull/${branch}`]
+    }
+    // refs/tags/
+    else if (upperRef.startsWith('REFS/TAGS/')) {
+      return [`+${commit}:${ref}`]
+    }
+    // Otherwise no destination ref
+    else {
+      return [commit]
+    }
+  }
+  // Unqualified ref, check for a matching branch or tag
+  else if (!upperRef.startsWith('REFS/')) {
+    return [
+      `+refs/heads/${ref}*:refs/remotes/origin/${ref}*`,
+      `+refs/tags/${ref}*:refs/tags/${ref}*`
+    ]
+  }
+  // refs/heads/
+  else if (upperRef.startsWith('REFS/HEADS/')) {
+    const branch = ref.substring('refs/heads/'.length)
+    return [`+${ref}:refs/remotes/origin/${branch}`]
+  }
+  // refs/pull/
+  else if (upperRef.startsWith('REFS/PULL/')) {
+    const branch = ref.substring('refs/pull/'.length)
+    return [`+${ref}:refs/remotes/pull/${branch}`]
+  }
+  // refs/tags/
+  else {
+    return [`+${ref}:${ref}`]
+  }
+}