@Nullable
  public String listNameIfOnlyOne(final @Nullable Change[] changes) {
    if (changes == null || changes.length == 0) {
      return null;
    }

    final Change first = changes[0];

    for (LocalChangeList list : myMap.values()) {
      final Collection<Change> listChanges = list.getChanges();
      if (listChanges.contains(first)) {
        // must contain all other
        for (int i = 1; i < changes.length; i++) {
          final Change change = changes[i];
          if (!listChanges.contains(change)) {
            return null;
          }
        }
        return list.getName();
      }
    }
    return null;
  }
  public boolean updateStep() {
    final MultiMap<VcsRoot, String> dirty = new MultiMap<VcsRoot, String>();
    final long oldPoint =
        System.currentTimeMillis()
            - (myVcsConfiguration.CHANGED_ON_SERVER_INTERVAL > 0
                ? myVcsConfiguration.CHANGED_ON_SERVER_INTERVAL * 60000
                : DISCRETE);

    synchronized (myLock) {
      // just copies myQueries MultiMap to dirty MultiMap
      for (VcsRoot root : myQueries.keySet()) {
        final Collection<String> collection = myQueries.get(root);
        for (String s : collection) {
          dirty.putValue(root, s);
        }
      }
      myQueries.clear();

      // collect roots for which cache update should be performed (by timestamp)
      final Set<VcsRoot> roots = new HashSet<VcsRoot>();
      for (Map.Entry<VcsRoot, Long> entry : myTs.entrySet()) {
        // ignore timestamp, as still remote changes checking is required
        // TODO: why not to add in roots anyway??? - as dirty is still checked when adding myChanged
        // files.
        if (!dirty.get(entry.getKey()).isEmpty()) continue;

        // update only if timeout expired
        final Long ts = entry.getValue();
        if ((ts == null) || (oldPoint > ts)) {
          roots.add(entry.getKey());
        }
      }

      // Add dirty files from those vcs roots, that
      // - needs to be update by timestamp criteria
      // - that already contain files for update through manually added requests
      for (Map.Entry<String, Pair<Boolean, VcsRoot>> entry : myChanged.entrySet()) {
        final VcsRoot vcsRoot = entry.getValue().getSecond();
        if ((!dirty.get(vcsRoot).isEmpty()) || roots.contains(vcsRoot)) {
          dirty.putValue(vcsRoot, entry.getKey());
        }
      }
    }

    if (dirty.isEmpty()) return false;

    final Map<String, Pair<Boolean, VcsRoot>> results =
        new HashMap<String, Pair<Boolean, VcsRoot>>();
    for (VcsRoot vcsRoot : dirty.keySet()) {
      // todo - actually it means nothing since the only known VCS to use this scheme is Git and now
      // it always allow
      // todo - background operations. when it changes, develop more flexible behavior here
      if (!vcsRoot.getVcs().isVcsBackgroundOperationsAllowed(vcsRoot.getPath())) continue;
      final TreeDiffProvider provider = vcsRoot.getVcs().getTreeDiffProvider();
      if (provider == null) continue;

      final Collection<String> paths = dirty.get(vcsRoot);
      final Collection<String> remotelyChanged =
          provider.getRemotelyChanged(vcsRoot.getPath(), paths);
      for (String path : paths) {
        // TODO: Contains invoked for each file - better to use Set (implementations just use List)
        // TODO: Why to store boolean for changed or not - why not just remove such values from
        // myChanged???
        results.put(path, new Pair<Boolean, VcsRoot>(remotelyChanged.contains(path), vcsRoot));
      }
    }

    final long curTime = System.currentTimeMillis();
    synchronized (myLock) {
      myChanged.putAll(results);
      for (VcsRoot vcsRoot : dirty.keySet()) {
        myTs.put(vcsRoot, curTime);
      }
    }

    return true;
  }
  public boolean updateStep(final AtomicSectionsAware atomicSectionsAware) {
    final MultiMap<VcsRoot, String> dirty = new MultiMap<VcsRoot, String>();
    final long oldPoint =
        System.currentTimeMillis()
            - (myVcsConfiguration.CHANGED_ON_SERVER_INTERVAL > 0
                ? myVcsConfiguration.CHANGED_ON_SERVER_INTERVAL * 60000
                : DISCRETE);

    synchronized (myLock) {
      for (VcsRoot root : myQueries.keySet()) {
        final Collection<String> collection = myQueries.get(root);
        for (String s : collection) {
          dirty.putValue(root, s);
        }
      }
      myQueries.clear();

      final Set<VcsRoot> roots = new HashSet<VcsRoot>();
      for (Map.Entry<VcsRoot, Long> entry : myTs.entrySet()) {
        if (!dirty.get(entry.getKey()).isEmpty()) continue;

        final Long ts = entry.getValue();
        if ((ts == null) || (oldPoint > ts)) {
          roots.add(entry.getKey());
        }
      }
      for (Map.Entry<String, Pair<Boolean, VcsRoot>> entry : myChanged.entrySet()) {
        final VcsRoot vcsRoot = entry.getValue().getSecond();
        if ((!dirty.get(vcsRoot).isEmpty()) || roots.contains(vcsRoot)) {
          dirty.putValue(vcsRoot, entry.getKey());
        }
      }
    }

    if (dirty.isEmpty()) return false;

    final Map<String, Pair<Boolean, VcsRoot>> results =
        new HashMap<String, Pair<Boolean, VcsRoot>>();
    for (VcsRoot vcsRoot : dirty.keySet()) {
      atomicSectionsAware.checkShouldExit();
      // todo - actually it means nothing since the only known VCS to use this scheme is Git and now
      // it always allow
      // todo - background operations. when it changes, develop more flexible behavior here
      if (!vcsRoot.vcs.isVcsBackgroundOperationsAllowed(vcsRoot.path)) continue;
      final TreeDiffProvider provider = vcsRoot.vcs.getTreeDiffProvider();
      if (provider == null) continue;

      final Collection<String> paths = dirty.get(vcsRoot);
      final Collection<String> remotelyChanged = provider.getRemotelyChanged(vcsRoot.path, paths);
      for (String path : paths) {
        results.put(path, new Pair<Boolean, VcsRoot>(remotelyChanged.contains(path), vcsRoot));
      }
    }

    final long curTime = System.currentTimeMillis();
    synchronized (myLock) {
      myChanged.putAll(results);
      for (VcsRoot vcsRoot : dirty.keySet()) {
        myTs.put(vcsRoot, curTime);
      }
    }

    return true;
  }