Feature request: support unpacking a cache generated with different UID/GID

[zyla]

When I try to unpack a cache created by an user with different UID or GID, I get this error:

cache-s3: /home/user/.stack: setOwnerAndGroup: permission denied (Operation not permitted)

This happens because tar-conduit tries to restore the original owner of the file when unpacking.

It's reasonable to ask why someone would need this. The use case is: we download caches from the CI system onto our development machines to speed up compilation after a branch change. The environment is compatible enough that it works, but sometimes we have different user or group IDs.

What would be the best way to implement this? I see several options:

• Copy-paste restoreFile from tar-conduit, and remove changing permissions. Not elegant.
• Modify the FileInfo passed to restoreFile and set UID/GID to the current user. This would work, but it seems like a hack.
• Extend tar-conduit, adding an option to skip setting UID/GID.