GetCommit.
        [Preview API] Retrieve a particular commit.
        :param str commit_id: The id of the commit.
        :param str repository_id: The id or friendly name of the repository. To use the friendly name, projectId must also be specified.
        :param str project: Project ID or project name
        :param int change_count: The number of changes to include in the result.
        :rtype: :class:`<GitCommit> <azure.devops.v5_1.git.models.GitCommit>`

def get_commit(self, commit_id, repository_id, project=None, change_count=None):
        """GetCommit.
        [Preview API] Retrieve a particular commit.
        :param str commit_id: The id of the commit.
        :param str repository_id: The id or friendly name of the repository. To use the friendly name, projectId must also be specified.
        :param str project: Project ID or project name
        :param int change_count: The number of changes to include in the result.
        :rtype: :class:`<GitCommit> <azure.devops.v5_1.git.models.GitCommit>`
        """
        route_values = {}
        if project is not None:
            route_values['project'] = self._serialize.url('project', project, 'str')
        if commit_id is not None:
            route_values['commitId'] = self._serialize.url('commit_id', commit_id, 'str')
        if repository_id is not None:
            route_values['repositoryId'] = self._serialize.url('repository_id', repository_id, 'str')
        query_parameters = {}
        if change_count is not None:
            query_parameters['changeCount'] = self._serialize.query('change_count', change_count, 'int')
        response = self._send(http_method='GET',
                              location_id='c2570c3b-5b3f-41b8-98bf-5407bfde8d58',
                              version='5.1-preview.1',
                              route_values=route_values,
                              query_parameters=query_parameters)
        return self._deserialize('GitCommit', response)