xfsdump doesn't allow levels beyond 0-9

Hi!

I've found, quite surprised, that xfsdump doesn't allow dump level numbers outside of the range [0-9]. Given that even storing that number requires a full byte (8 bits), it boggles the mind why more numbers aren't supported. The usefulness of supporting more numbers (24? even 255...) is for taking hourly delta snapshots of live filesystems using xfsdump as a backup measure.

With a simple script one can write a backup that takes a full dump (level 0) of the filesystem for the first backup of a given date, and all other backups during that day are incrementals (levels are > 0 ... i.e. the hour of the day the backup is taken). However, given that the tool only supports [0-9] as the backup level, this seems like an arbitrary limitation.

Is there a real, technical limitation that this level is adhering to?

Cheers!
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ProblemType: Bug
ApportVersion: 2.20.10-0ubuntu27
Architecture: amd64
AudioDevicesInUse:
 USER PID ACCESS COMMAND
 /dev/snd/controlC0: gdm 3277 F.... pulseaudio
                      diego 3916 F.... pulseaudio
 /dev/snd/pcmC0D0p: diego 3916 F...m pulseaudio
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DistroRelease: Ubuntu 19.04
InstallationDate: Installed on 2019-04-20 (26 days ago)
InstallationMedia: Ubuntu 19.04 "Disco Dingo" - Release amd64 (20190416)
MachineType: ASUS All Series
NonfreeKernelModules: nvidia_modeset nvidia
Package: linux (not installed)
ProcFB: 0 EFI VGA
ProcKernelCmdLine: BOOT_IMAGE=/vmlinuz-5.0.0-13-generic root=UUID=1e9e8db1-15c8-4369-b27b-1a797cfe8561 ro quiet splash ipv6.disable=1 crashkernel=512M-:192M vt.handoff=1
ProcVersionSignature: Ubuntu 5.0.0-13.14-generic 5.0.6
PulseList:
 Error: command ['pacmd', 'list'] failed with exit code 1: Home directory not accessible: Permission denied
 No PulseAudio daemon running, or not running as session daemon.
RelatedPackageVersions:
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 linux-backports-modules-5.0.0-13-generic N/A
 linux-firmware 1.178.1
RfKill:
 3: hci0: Bluetooth
  Soft blocked: no
  Hard blocked: no
Tags: disco
Uname: Linux 5.0.0-13-generic x86_64
UpgradeStatus: No upgrade log present (probably fresh install)
UserGroups:

_MarkForUpload: True
dmi.bios.date: 09/15/2017
dmi.bios.vendor: American Megatrends Inc.
dmi.bios.version: 3801
dmi.board.asset.tag: Default string
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dmi.board.vendor: ASUSTeK COMPUTER INC.
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