What happens on ext4?

It refuses and says why. ext4 has no way to share blocks between two files, so every copy would cost the full size.

It refuses and says why. ext4 has no way to share blocks between two files, so every copy would cost the full size.

gitto: copying here costs the full size, so a clone would too.
      macOS needs APFS; Linux needs btrfs, XFS with reflink=1, or OpenZFS 2.2+.
      ext4 and tmpfs cannot share blocks at all.