Warn when downloading/pulling older versions of files

[mpadge]

With respectful acknowledgment of your mistrust of timestamps, one place where these would actually be useful would be in order to implement a warning when downloading/pulling older versions of files, and consequently overwriting newer versions that may have since been created locally. That would be a really useful safety mechanism (for my current workflow at least). We're throwing files between lots of different people doing different tasks, and inadvertent overwrites do happen, and are potentially painful.

[cboettig]

Yeah, overwrites are definitely and issue so that's a good idea.

Maybe we should go one further and simply provide the option of use_timestamps = FALSE/warn,/TRUE to push/pull. warn would do as you say, FALSE is the current behavior, and TRUE would only push/pull those files with differing hashes AND older timestamps.

Perhaps my mistrust of timestamps is not so warranted -- mostly arises from the fact that switching branches changes the timestamp, and from work on poorly maintained servers with drifting clocks long ago. I guess since these files are not git managed, they would not be impacted by the latter. A more empirically grounded opinion on timestamps might be called for. (I agree that managing the hash tree a la git is the 'real' solution to version tracking, but I'm not going to implement that by hand).

[mpadge]

That sounds like a great solution. And yeah, the whole idea of piggyback is to avoid clogging up repos with the piggybacked files, so one can surely assume they very generally won't be part of a git tree, so should not have time stamps altered by any git operations. This would - for me - be a great boost!

[cboettig]

timestamp behavior now the default for upload / download