Preserve timestamps of files transfered to/from cache

[kskalski]

I'm having trouble with using the extracted -> injected cache content in Rust environment. It appears as the compilation artifacts are ignored/invalidated by cargo tool (I managed to successfully cache and re-use the downloaded dependencies, so the set-up itself seems to kind of work).
My current guess is that modifying timestamps during "dance" is making the files ignored.

In any case I think preserving timestamps would be a nice to have feature. It should be possible to achieve by

• augmenting cp with -p flag (-p same as --preserve=mode,ownership,timestamps): https://askubuntu.com/questions/1040885/copy-a-file-and-keep-the-same-timestamp-of-the-original-file
• possibly also augmenting tar to increase precision of timestamps by -H posix: https://unix.stackexchange.com/questions/397130/tar-how-to-preserve-timestamps-down-to-more-than-a-second-of-precision