async backupMergeStatus() {
    debugLog('Backing up merge state...')
    await Promise.all([
      readFile(this.mergeHeadFilename).then((buffer) => (this.mergeHeadBuffer = buffer)),
      readFile(this.mergeModeFilename).then((buffer) => (this.mergeModeBuffer = buffer)),
      readFile(this.mergeMsgFilename).then((buffer) => (this.mergeMsgBuffer = buffer)),
    ])
    debugLog('Done backing up merge state!')
  }
Save meta information about ongoing git merge