Cannot get binaries for a multibuild package without checkout

[Michal Suchánek]

Describe the bug
Cannot get binaries for a multibuild package without checkout

Versions

• Operating system: openSUSE Leap 15.5
• Packages: osc-1.6.2-lp155.2.1.noarch

To Reproduce

hramrach@localhost:~> ibs getbinaries -d i-i/reduced home:michals:kernel-test-15 installation-images standard ppc64le
WARNING: Ignoring config '~/.config/osc/oscrc' in XDG location, loading an existing config from ~/.oscrc instead
         To fix this, remove '~/.oscrc'
no binaries found: Either the package installation-images does not exist or no binaries have been built.
hramrach@localhost:~> ibs getbinaries -d i-i/reduced -M SLES home:michals:kernel-test-15 installation-images standard ppc64le
WARNING: Ignoring config '~/.config/osc/oscrc' in XDG location, loading an existing config from ~/.oscrc instead
         To fix this, remove '~/.oscrc'
usage: osc [global opts] getbinaries [-h] [-d DIR] [-M FLAVOR] [--sources]
                                     [--debuginfo] [--ccache]
osc [global opts] getbinaries: error: The -M/--multibuild-package option can be only used from a package checkout.

Expected behavior

Can specify package flavor when package is specified

Screenshots, console outputs
If applicable, add screenshots or console outputs to help explain your problem.

Additional context

ibs getbinaries -d i-i/reduced home:michals:kernel-test-15 installation-images:SLES standard ppc64le

works but that's a very inconsistent interface, and the error does not provide the required information, and in the help text it's buried in description of the -M option.