private boolean tag(
      HttpServletRequest request,
      HttpServletResponse response,
      Repository db,
      String commitId,
      String tagName,
      boolean isRoot)
      throws JSONException, URISyntaxException, ServletException {
    Git git = new Git(db);
    RevWalk walk = new RevWalk(db);
    try {
      ObjectId objectId = db.resolve(commitId);
      RevCommit revCommit = walk.lookupCommit(objectId);
      walk.parseBody(revCommit);

      GitTagHandlerV1.tag(git, revCommit, tagName);

      URI cloneLocation =
          BaseToCloneConverter.getCloneLocation(
              getURI(request), BaseToCloneConverter.COMMIT_REFRANGE);
      Commit commit = new Commit(cloneLocation, db, revCommit, null);
      JSONObject result = commit.toJSON();
      OrionServlet.writeJSONResponse(
          request, response, result, JsonURIUnqualificationStrategy.ALL_NO_GIT);
      return true;
    } catch (IOException e) {
      return statusHandler.handleRequest(
          request,
          response,
          new ServerStatus(
              IStatus.ERROR,
              HttpServletResponse.SC_INTERNAL_SERVER_ERROR,
              "An error occured when tagging.",
              e));
    } catch (GitAPIException e) {
      return statusHandler.handleRequest(
          request,
          response,
          new ServerStatus(
              IStatus.ERROR,
              HttpServletResponse.SC_INTERNAL_SERVER_ERROR,
              "An error occured when tagging.",
              e));
    } catch (CoreException e) {
      return statusHandler.handleRequest(
          request,
          response,
          new ServerStatus(
              IStatus.ERROR,
              HttpServletResponse.SC_INTERNAL_SERVER_ERROR,
              "An error occured when tagging.",
              e));
    } finally {
      walk.dispose();
    }
  }
  private boolean handleGetCommitBody(
      HttpServletRequest request,
      HttpServletResponse response,
      Repository db,
      String ref,
      String pattern)
      throws IOException, ServletException, CoreException {
    ObjectId refId = db.resolve(ref);
    if (refId == null) {
      String msg = NLS.bind("Failed to get commit body for ref {0}", ref);
      return statusHandler.handleRequest(
          request,
          response,
          new ServerStatus(IStatus.ERROR, HttpServletResponse.SC_BAD_REQUEST, msg, null));
    }
    RevWalk walk = new RevWalk(db);
    walk.setTreeFilter(
        AndTreeFilter.create(
            PathFilterGroup.createFromStrings(Collections.singleton(pattern)),
            TreeFilter.ANY_DIFF));
    RevCommit revCommit = walk.parseCommit(refId);
    walk.dispose();

    Commit commit = new Commit(null /* not needed */, db, revCommit, pattern);
    ObjectStream stream = commit.toObjectStream();
    if (stream == null) {
      String msg = NLS.bind("Commit body for ref {0} not found", ref);
      return statusHandler.handleRequest(
          request,
          response,
          new ServerStatus(IStatus.ERROR, HttpServletResponse.SC_NOT_FOUND, msg, null));
    }
    IOUtilities.pipe(stream, response.getOutputStream(), true, false);

    return true;
  }
  @Override
  protected boolean handlePost(RequestInfo requestInfo) throws ServletException {
    String gitSegment = requestInfo.gitSegment;
    HttpServletRequest request = requestInfo.request;
    HttpServletResponse response = requestInfo.response;
    Repository db = requestInfo.db;
    String pattern = requestInfo.relativePath;
    JSONObject requestObject = requestInfo.getJSONRequest();
    try {
      String commitToMerge = requestObject.optString(GitConstants.KEY_MERGE, null);
      if (commitToMerge != null) {
        boolean squash = requestObject.optBoolean(GitConstants.KEY_SQUASH, false);
        return merge(request, response, db, commitToMerge, squash);
      }

      String commitToRebase = requestObject.optString(GitConstants.KEY_REBASE, null);
      String rebaseOperation = requestObject.optString(GitConstants.KEY_OPERATION, null);
      if (commitToRebase != null) {
        return rebase(request, response, db, commitToRebase, rebaseOperation);
      }

      String commitToCherryPick = requestObject.optString(GitConstants.KEY_CHERRY_PICK, null);
      if (commitToCherryPick != null) {
        return cherryPick(request, response, db, commitToCherryPick);
      }

      String commitToRevert = requestObject.optString(GitConstants.KEY_REVERT, null);
      if (commitToRevert != null) {
        return revert(request, response, db, commitToRevert);
      }

      String newCommit = requestObject.optString(GitConstants.KEY_COMMIT_NEW, null);
      if (newCommit != null) return identifyNewCommitResource(request, response, db, newCommit);

      String reviewReqLogin = requestObject.optString(GitConstants.KEY_REVIEW_REQ_NOTIFY_LOGIN);
      if (reviewReqLogin != null && reviewReqLogin.length() != 0) {
        String reviewReqUrl = requestObject.optString(GitConstants.KEY_REVIEW_REQ_URL);
        String ReviewReqCommit = requestObject.optString(GitConstants.KEY_REVIEW_REQ_COMMIT);
        String ReviewReqAuthorName =
            requestObject.optString(GitConstants.KEY_REVIEW_REQ_AUTHOR_NAME);
        String ReviewMessage = requestObject.optString(GitConstants.KEY_REVIEW_REQ_MESSAGE);
        return sendNotification(
            request,
            response,
            db,
            reviewReqLogin,
            ReviewReqCommit,
            reviewReqUrl,
            ReviewReqAuthorName,
            ReviewMessage);
      }

      ObjectId refId = db.resolve(gitSegment);
      if (refId == null || !Constants.HEAD.equals(gitSegment)) {
        String msg = NLS.bind("Commit failed. Ref must be HEAD and is {0}", gitSegment);
        return statusHandler.handleRequest(
            request,
            response,
            new ServerStatus(IStatus.ERROR, HttpServletResponse.SC_BAD_REQUEST, msg, null));
      }

      String message = requestObject.optString(GitConstants.KEY_COMMIT_MESSAGE, null);
      if (message == null || message.isEmpty()) {
        return statusHandler.handleRequest(
            request,
            response,
            new ServerStatus(
                IStatus.ERROR,
                HttpServletResponse.SC_BAD_REQUEST,
                "Missing commit message.",
                null));
      }

      Git git = new Git(db);
      CommitCommand cc = git.commit();
      Config config = git.getRepository().getConfig();

      boolean amend =
          Boolean.parseBoolean(requestObject.optString(GitConstants.KEY_COMMIT_AMEND, null));
      boolean insertChangeId =
          GitUtils.isGerrit(config)
              || Boolean.parseBoolean(requestObject.optString(GitConstants.KEY_CHANGE_ID, null));

      String committerName = requestObject.optString(GitConstants.KEY_COMMITTER_NAME, null);
      String committerEmail = requestObject.optString(GitConstants.KEY_COMMITTER_EMAIL, null);
      String authorName = requestObject.optString(GitConstants.KEY_AUTHOR_NAME, null);
      String authorEmail = requestObject.optString(GitConstants.KEY_AUTHOR_EMAIL, null);

      // workaround of a bug in JGit which causes invalid
      // support of null values of author/committer name/email, see bug 352984
      PersonIdent defPersonIdent = new PersonIdent(db);
      if (committerName == null) committerName = defPersonIdent.getName();
      if (committerEmail == null) committerEmail = defPersonIdent.getEmailAddress();
      if (authorName == null) authorName = committerName;
      if (authorEmail == null) authorEmail = committerEmail;
      cc.setCommitter(committerName, committerEmail);
      cc.setAuthor(authorName, authorEmail);
      if (insertChangeId) cc.setInsertChangeId(true);

      // support for committing by path: "git commit -o path"
      if (!pattern.isEmpty()) {
        cc.setOnly(pattern);
      }

      try {
        // "git commit [--amend] -m '{message}' [-a|{path}]"
        RevCommit lastCommit = cc.setAmend(amend).setMessage(message).call();

        URI cloneLocation =
            BaseToCloneConverter.getCloneLocation(
                getURI(request), BaseToCloneConverter.COMMIT_REFRANGE);
        Commit commit = new Commit(cloneLocation, db, lastCommit, pattern);
        JSONObject result = commit.toJSON();
        OrionServlet.writeJSONResponse(
            request, response, result, JsonURIUnqualificationStrategy.ALL_NO_GIT);
        return true;
      } catch (GitAPIException e) {
        return statusHandler.handleRequest(
            request,
            response,
            new ServerStatus(
                IStatus.ERROR,
                HttpServletResponse.SC_BAD_REQUEST,
                "An error occured when commiting.",
                e));
      } catch (UnmergedPathException e) {
        return statusHandler.handleRequest(
            request,
            response,
            new ServerStatus(
                IStatus.ERROR,
                HttpServletResponse.SC_INTERNAL_SERVER_ERROR,
                "An internal error occured when commiting.",
                e));
      }
    } catch (Exception e) {
      return statusHandler.handleRequest(
          request,
          response,
          new ServerStatus(
              IStatus.ERROR,
              HttpServletResponse.SC_INTERNAL_SERVER_ERROR,
              "An error occured when requesting a commit info.",
              e));
    }
  }