Keeping original timestamps + building

As posted in
https://stackoverflow.com/questions/50076004/version-control-system-that-keeps-original-timestamps
, it would be very good to keep timestamps of files across copies as the true modification time of their contents. As of now, every pull uses "now" as the timestamp.

Answer
https://stackoverflow.com/a/50076070/2707864
suggests a way of achieving it:

1. pull modified files with "now" as timestamp (as bzr does), but also pull the information about true modification time of those files and store it.
2. Force rebuilding (if using bzr for software development or other build system).
3. touch modified files with the known true modification times.

This will leave the local copy in ideal conditions. Moreover, actions (2+3) could be encapsulated into an "enhanced build" action.