/**
  * Executes 'git push' for the given roots to push. Returns the list of errors if there were any.
  */
 private List<VcsException> executePushCommand(final Collection<Root> rootsToPush) {
   final ArrayList<VcsException> errors = new ArrayList<VcsException>();
   for (Root r : rootsToPush) {
     GitLineHandler h = new GitLineHandler(myProject, r.root, GitCommand.PUSH);
     String src = r.commitToPush != null ? r.commitToPush : r.currentBranch;
     h.addParameters("-v", r.remoteName, src + ":" + r.remoteBranch);
     GitPushUtils.trackPushRejectedAsError(
         h, "Rejected push (" + r.root.getPresentableUrl() + "): ");
     errors.addAll(GitHandlerUtil.doSynchronouslyWithExceptions(h));
   }
   return errors;
 }
  /**
   * Load VCS roots
   *
   * @param project the project
   * @param roots the VCS root list
   * @param exceptions the list of of exceptions to use
   * @param fetchData if true, the data for remote is fetched.
   * @return the loaded information about vcs roots
   */
  private static List<Root> loadRoots(
      final Project project,
      final List<VirtualFile> roots,
      final Collection<VcsException> exceptions,
      final boolean fetchData) {
    final ArrayList<Root> rc = new ArrayList<Root>();
    for (VirtualFile root : roots) {
      try {
        Root r = new Root();
        rc.add(r);
        r.root = root;
        GitBranch b = GitBranch.current(project, root);
        if (b != null) {
          r.currentBranch = b.getFullName();
          r.remoteName = b.getTrackedRemoteName(project, root);
          r.remoteBranch = b.getTrackedBranchName(project, root);
          if (r.remoteName != null) {
            if (fetchData && !r.remoteName.equals(".")) {
              GitLineHandler fetch = new GitLineHandler(project, root, GitCommand.FETCH);
              fetch.addParameters(r.remoteName, "-v");
              Collection<VcsException> exs = GitHandlerUtil.doSynchronouslyWithExceptions(fetch);
              exceptions.addAll(exs);
            }
            GitBranch tracked = b.tracked(project, root);
            assert tracked != null : "Tracked branch cannot be null here";
            final boolean trackedBranchExists = tracked.exists(root);
            if (!trackedBranchExists) {
              LOG.info("loadRoots tracked branch " + tracked + " doesn't exist yet");
            }

            // check what remote commits are not yet merged
            if (trackedBranchExists) {
              GitSimpleHandler toPull = new GitSimpleHandler(project, root, GitCommand.LOG);
              toPull.addParameters(
                  "--pretty=format:%H", r.currentBranch + ".." + tracked.getFullName());
              toPull.setNoSSH(true);
              toPull.setStdoutSuppressed(true);
              StringScanner su = new StringScanner(toPull.run());
              while (su.hasMoreData()) {
                if (su.line().trim().length() != 0) {
                  r.remoteCommits++;
                }
              }
            }

            // check what local commits are to be pushed
            GitSimpleHandler toPush = new GitSimpleHandler(project, root, GitCommand.LOG);
            // if the tracked branch doesn't exist yet (nobody pushed the branch yet), show all
            // commits on this branch.
            final String revisions =
                trackedBranchExists
                    ? tracked.getFullName() + ".." + r.currentBranch
                    : r.currentBranch;
            toPush.addParameters("--pretty=format:%H%x20%ct%x20%at%x20%s%n%P", revisions);
            toPush.setNoSSH(true);
            toPush.setStdoutSuppressed(true);
            StringScanner sp = new StringScanner(toPush.run());
            while (sp.hasMoreData()) {
              if (sp.isEol()) {
                sp.line();
                continue;
              }
              Commit c = new Commit();
              c.root = r;
              String hash = sp.spaceToken();
              String time = sp.spaceToken();
              c.revision = new GitRevisionNumber(hash, new Date(Long.parseLong(time) * 1000L));
              c.authorTime = sp.spaceToken();
              c.message = sp.line();
              c.isMerge = sp.line().indexOf(' ') != -1;
              r.commits.add(c);
            }
          }
        }
      } catch (VcsException e) {
        exceptions.add(e);
      }
    }
    return rc;
  }