Feature Request: Compare versions between two groups but not within a group

[michaelcadilhac]

I have access to all the iterations of student A's work: subA.1.c, ..., subA.999.c. Similarly, I have access to all the iterations of student B, C, D, etc.

I wish to compare all of A's versions with any other version, but, crucially, avoid comparing A's versions with another of A's versions.

Proposals:

• Add an option --has-versioning, with a pre-defined format for versions (e.g., file.c, file.c.1, file.c.2, file.c.3).
• Add an option --has-versioning, with a glob-like versioning template --version-filename='*.#.c' where # corresponds to version number.
• Add an option --same-user-cmp=prog where prog would be run with two filenames, to test if two files are from the same user.