store the results in some common branch in repo

[goyalyashpal]

Current

The submit/courses page lists all the latest/all scores for all the problems and also gives button to export the individual problems scores.

Proposal

The proposal is to automatically append the results for each complete execution of submit50 in a csv file to a common branch (say "grades") of the student's ms50 repo.

That way, students can use their knowledge of SQL from x/*/week/7 or the like to analyse their grades themselves.

To avoid students from messing up with the format of the file, students shouldn't be given write access to that branch.