Support FS-specific attributes / flags #9549
Description
This is a meta-issue pointing to some similar other ones (so that we can reduce the number of open issues).
borg supports a few filesystem flags (aka bsdflags), esp. the more popular ones and the ones present on most platforms.
Beyond that, some filesystems have special attributes / flags:
- Support FAT attributes #2805
- btrfs +C (nocow) flag considerations #1557
- support fs specific flags? (e.g. ext4) #618
It is unclear whether borg should support such fs-specific flags / attributes.
This is not just about adding some metadata to the archived item, but also:
- borg would need to detect the fs to know which attributes / flags it can extract. it might even depend on the version of the filesystem...
- would need fs-specific code in borg (we try to avoid this)
- cross-filesystem differences (would borg try to map flags between filesystems?)
- it is sometimes not easy to deal with those flags, especially the time when they need to get set or how they influence other file metadata (e.g. timestamps)
- ...