Introduction

Nerfherder is a collection of Python hacks for grading GitHub Classroom repositories. (So-named because it is a flaky thing that wrangles other flaky things.)

Requirements

• Python 3
• git commandline tools
• PyGithub https://pypi.python.org/pypi/PyGithub/1.35

Dependency Installation

You need the git command-line tools. On Debian- or Ubuntu-based Linux environments, use

[~]$ sudo apt install git

The following command should prepare your Python environment:

[~]$ pip3 install PyGithub keyring

Cloning Student Repositories

Assuming we have cloned the nerherder repo to ~/nerfherder, and we already created a directory for grading at ~/grading,

[~/grading]$ ~/nerfherder/clone-organization kevinwortman CSUF-CPSC-335-FA18

(Note: the first argument is a GitHub username, not email address, so there is no @domain.com; and, give the organization name, not the URL to the organization, so there is no https:// .)

This will prompt you for your GitHub password once, and then pull each repo owned by the GitHub organization CSUF-CPSC-335-FA18.

By default this command will skip repos that are already present locally. This is an optimization to avoid re-downloading old submissions which are unlikely to change after they have already been graded. If instead you want to download every repository, including ones that are already here, use the --replace switch.

[~/grading]$ ~/nerfherder/clone-organization kevinwortman CSUF-CPSC-335-FA18 --replace

Importing Groups to Moodle

Our workflow uses GitHub Classroom to assign and collect programming projects, and Moodle for grade calculation and distribution. Ordinarily we allow students to work in groups of 1-3 on these projects. Moodle supports team assignments, but there is no direct link between the user account and group information in GitHub, and the notion of teams in Moodle. It might be possible to create such a link using Moodle`s PHP API, but we presently do not have the resources to undertake that project.

In the mean time, the create-groups-csv and group-member-emails scripts semi-automate the process of exporting GitHub group information into a format that Moodle understands.

We require students to indicate their chosen groups by editing a README.md that contains their school-issued email addresses, and no other email addresses. This approach is not quite ideal since it involves unstructured data, but it works.

These tools expect that you use either GitHub Classroom Assistant, or the clone-organization script in this repository, to download submissions. These tools create a submission directory which is a directory that contains cloned student repositories.

create-groups-csv examines a submission directory, filters for actual git repos that contain a .git, and creates a CSV file that lists each repo name as a Moodle group name. You may give an optional prefix that is applied to all group names, we use something like project-1 and project-2 so that groups for each project are separated alphabetically. This CSV file is understood by the Import Groups feature in Moodle.

Importing these groups will make them exist in Moodle, but each group will be empty with no students in the group. You need to use the Moodle web interface to assign students into these groups.

group-member-emails finds apparent git repos inside a submission directory, and for each, searches README.md for email addresses (matched by a regular expression), and prints out the results in a compact format.

You can run group-member-emails, leave the results in a terminal window, open a browser to the groups page in Moodle, and use the email addresses to find student accounts and assign them into groups. While this is somewhat tedious, it is still more agreeable than doing this entire process manually, or leaving Moodle unaware of groups.

MOSS Plagiarism Detection

MOSS is a web service that identifies similarities in source code which might indicate plagiarism.

In order to use MOSS, you will need to create an account, and in the last step of that process the server will email a submission script. The MOSS authors ask for that script to not be publicized, so we are not duplicating the script's functionality. Instead we created moss-submit which is a lightweight glue-code script that makes it easier to submit code from a GitHub-based submission directory.

Per the YAGNI principle, moss-submit is based upon some simplifying assumptions:

• student submissions are organized in a submission directory (as defined above)
• there is a repo with starter code, outside the submission directory, that has been cloned locally
• only one source file (per repo) is checked for similarity, i.e. there is one file such as main.cpp that contains all substantial student work
• you have already created a MOSS account and followed their instructions to save the submission script locally

If you are checking a C++ assignment, where students edit implementation.hpp, your MOSS script is in ~/Documents/moss, your starter code is cloned to ~/Documents/project1-starter, and you have downoaded student submission repos to ~/Documents/project1-submissions, then the following command will submit to MOSS:

[~]$ ~/nerfherder/moss-submit --filename implementation.hpp --moss ~/Documents/moss --skeleton ~/Documents/project1-starter --dir ~/Documents/project1-submissions

As described in the online help, you can override the programming language with the --language flag.