"Copy Newer" and "Copy Different" ???

[sjk]

There are situations when files appear to be "newer" than their modification times from a user's perspective. The download example was one case. Another might be where a directory hierarchy is reverted to a chronologically older copy which is then considered the "newer" version.

In situations like that it's risky relying on file modification times for backups, which is how I understand Copy Newer to work. From your description it sounds like Copy Different includes "inode is newer" files (detected with a st_ctimespec or equivalent change), which is the behavior I'm mostly interested in.

Now, it's debatable which method makes "more sense" to users. Seems to me Copy Different is generally more natural because it's relative to the user's perception of when files have actually changed, e.g. the content differs, irregardless of modification times.

Just because files have changed doesn't necessarily make them newer, which might cause Copy Newer to produce inaccurate, unexpected results. Knowing whether files have changed in "my" time or "their" time can be confusing.

I think your reworked explanation posted here (which I didn't notice 'til after my post) makes the Newer vs. Different distinction quite clear. Maybe some usage example for both would help in understanding which might be useful in which situations and for avoiding unexpected results like I've just tried to describe.