feat: mv: preserve attributes when moving

[fdncred]

Feature Request related to #6002

It may be helpful to some users for mv to be able to maintain attributes like timestamps when moving files to/from internal/external drives, or really just moving files/folders in general.

A nushell user requested this functionality. Here's the linked issue. https://github.com/nushell/nushell/issues/11943

Kind of related with cp https://github.com/uutils/coreutils/issues/4192

[mtimaN]

Does this issue only occur when moving files between different drives? I tried it locally and uutils mv maintains the access, modify and birth timestamps.

$ touch a
$ mkdir b
$ stat a
  File: a
  Size: 0         	Blocks: 0          IO Block: 4096   regular empty file
Device: 10304h/66308d	Inode: 2097353     Links: 1
Access: (0664/-rw-rw-r--)  Uid: ( 1000/  mtiman)   Gid: ( 1000/  mtiman)
Access: 2024-02-24 17:21:58.597614640 +0200
Modify: 2024-02-24 17:21:58.597614640 +0200
Change: 2024-02-24 17:21:58.597614640 +0200
 Birth: 2024-02-24 17:21:58.597614640 +0200
$ ../target/debug/coreutils mv a b/
$ stat b/a 
  File: b/a
  Size: 0         	Blocks: 0          IO Block: 4096   regular empty file
Device: 10304h/66308d	Inode: 2097353     Links: 1
Access: (0664/-rw-rw-r--)  Uid: ( 1000/  mtiman)   Gid: ( 1000/  mtiman)
Access: 2024-02-24 17:21:58.597614640 +0200
Modify: 2024-02-24 17:21:58.597614640 +0200
Change: 2024-02-24 17:22:18.265634719 +0200
 Birth: 2024-02-24 17:21:58.597614640 +0200

Let me know if I misunderstood anything.

[fdncred]

@mtimaN The original issue is linked above where @sgon00 talks about moving files to an external drive.

[sgon00]

@mtimaN yeah, this issue only happens when moving files to/from external drives. I am running Ubuntu 23.10. Both internal drive filesystem and external drive filesystem are ext4. (Btw, they are both LUKS encrypted, but I don't think that does matter).

Edited: The external drive is connected via type-c USB port.

[mtimaN]

I think this issue is exceeding my expertise.. I don't get why uutils' mv would work differently if the destination is on another drive.

[tertsdiepraam]

@mtimaN It's probably because we try to use std::fs::rename, which can't move between file systems and then we fall back to alternative implementation if that fails. So the problem is with that alternative implementation.

[mtimaN]

@mtimaN It's probably because we try to use std::fs::rename, which can't move between file systems and then we fall back to alternative implementation if that fails. So the problem is with that alternative implementation.

Thanks! I took a better look at the code and identified the alternative implementation. However, it seems that uutils' implementation yields the same results as GNU's so I don't think that it should be changed.

In the case of adding a new flag for treating this option, I tried using fs::FileTimes but it doesn't seem to work when trying to change the accessed time.