Add factory functions to distinguish between when the owner of the File
wants to transfer ownership to the new IPC object (adopt) or to send a
copy of the same fd to the IPC peer (clone).
This behavior is more intuitive than the previous behavior. Previously,
an IPC::File would default to a shallow clone of the file descriptor,
only *actually* calling dup(2) for the fd when encoding or it into an
IPC MessageBuffer. Now the dup(2) for the fd is explicit in the clone_fd
factory function.
This prevents fd leaks when the user of the API forgets to pass
CloseAfterSending to IPC::File. Since we are calling leak_fd in the
constructor, we want it to also take care of closing.
SPDX License Identifiers are a more compact / standardized
way of representing file license information.
See: https://spdx.dev/resources/use/#identifiers
This was done with the `ambr` search and replace tool.
ambr --no-parent-ignore --key-from-file --rep-from-file key.txt rep.txt *
If you don't need a file descriptor after sending it to someone over
IPC, construct it with IPC::File(fd, IPC::File::CloseAfterSending)
and LibIPC will take care of it for you. :^)
When receiving a file descriptor over IPC, the receiver must now call
take_fd() on the IPC::File to take over the descriptor. Otherwise,
IPC::File will close the file on destruction.
