Recording TIMESTAMPs in distinfo for reproducible builds work

[Derek (freebsd lists)]

On 16-05-12 02:08 PM, Ed Maste wrote:
> Baptiste and I have been looking at reproducible builds in the FreeBSD
> ports tree, and one thing we'll need is a consistent timestamp that
> doesn't change when a port is rebuilt without changes.
>

Just wondering if any work has gone into consuming these 
timestamps in the tools?

Specifically, looking at tar(1) from -head, I see that it doesn't 
current support the -mtime flag that GNU tar does, to be able to 
set the timestamp on all of the files being archived.

Any thoughts on what the canonical way will be: e.g. a pass in 
advance with find/touch or if BSD tar is planned to support this 
internally?

Thanks!
Derek