v6.12

• subvolume delete: add new option to do recursive subvolume deletion (for regular user delete only accessible subvolumes)
• mkfs:
  • new option --subvol to create subvolumes in given paths, read-write, read-only and default
  • add hard link detection support for --rootdir option
• fixes:
  • receive: message verbosity fixes
  • check: fix false positive report of missing checksum for extent holes
  • check: handle compressed extents when checking tree log
  • when asking Y/N user questions, flush the terminal so the question is displayed (e.g. btrfstune -S)
• other
  • code refactoring, error handling
  • python packaging fixes
  • documentation updates
  • new tests