Which files are required to copy / version my Quartus project?
I can't answer specifically about github. But I can answer on what you should archive from a Quartus II project, be it into a version control repository, ZIP file or whatever...

You need to archive all of the following that you have:


   qpf             Quartus Project  File
   qsf             Quartus Settings File
   bdf/bsf/vhd/v   design source files
   sdc             Timequest constraints file
   sof/pof         programming files (whichever one you use)

The list gets bigger if you've used Qsys. You haven't, and many projects don't ever, so I'll leave that to one side here.

You could archive the report files, some do...but I wouldn't. They run megabytes, or tens of, and can be regenerated. From the same Quartus/SP version and the same source files and input files above, you will get the same synthesis run and and configuration files produced along the same reports.

Don't archive any of the subdirectories such as 'db' - they're working directories, created during synthesis. The only exception is an 'output_files' or suchlike directory containing pofs/sofs, if you've selected the qsf/GUImenu option to store these in a subdirectory which you haven't here.