private File checkBaseline(DiskStore diskStore) {
    File baselineDir = memberBackupLocationDir.toFile();

    if (!baselineDir.exists()) {
      // hmmm, did this member have a restart? Determine which member dir might be a match for us
      baselineDir = findBaselineForThisMember(memberBackupLocationDir.getParent(), diskStore);
    }

    if (null != baselineDir) {
      // check for existence of INCOMPLETE_BACKUP_FILE file
      File incompleteBackup = new File(baselineDir, INCOMPLETE_BACKUP_FILE);
      if (incompleteBackup.exists()) {
        baselineDir = null;
      }
    }
    return baselineDir;
  }
Performs a sanity check on the baseline directory for incremental backups. If a baseline
directory exists for the member and there is no INCOMPLETE_BACKUP_FILE file then return the
data stores directory for this member.
geode-core/src/main/java/org/apache/geode/internal/cache/backup/FileSystemIncrementalBackupLocation.java