APFS features

[M0rtenB]

Utilization of APFS features such as instantaneous everywhere folder sizes and copy-on-write copying as default.

[mikekazakov]

Thank you for your suggestion. This feature would be a great addition, but I have limited capacity to work on new ideas at the moment. If you’re interested in helping implement it, I’d be happy to support you through the process.

[M0rtenB]

I’d love to, but I don’t know any C++, I’m a Python man.
Copilot seems to suggest it’s just a matter of calling another system call “clonefile” (for the copy-on-write part), so maybe not so complicated? Do you foresee trouble?

[mikekazakov]

C++ isn't Mayan scripture either ;)
In the end, it's a syscall of sorts - maybe via clonefile or something more direct. Don't foresee major trouble, it's just work to be done:

• Decide when to call it and when not to - both source and destination have to be on a filesystem that supports cloning, and it has to be the same volume.
• Provide opt-in/opt-out options, pass them through the program and obey them.
• Implement a UI to control these options, including wording in two languages.
• Cover the functionality with tests.

[M0rtenB]

Looking at https://wadetregaskis.com/copy-on-write-on-apfs/
It seems the C library function copyfile with an argument of COPYFILE_CLONE does the fall-back for you, i.e. tests to see if both source and dest are on the same APFS volume, and if not, it falls back to regular non-copy-on-write copying.
Does this not simplify the matter significantly?

[mikekazakov]

Well, if the idea is to migrate a large chunk of CopyingJob.cpp to copyfile, then yes, but that's not something I'considering nor want to spend my time on.
Adding a specific codepath for file cloning via clonefile/clonefileat/fclonefileat seems to be the right approach.