getbinaries -M not always functional

[jengelh]

Describe the bug

$ osc co openSUSE:Factory/ffmpeg-6 && cd openSUSE/Factory/ffmpeg-6/
...

$ osc getbinaries openSUSE:Factory/ffmpeg-6 -M ffmpeg-6-mini standard x86_64
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.

$ osc getbinaries openSUSE:Factory/ffmpeg-6:ffmpeg-6-mini standard x86_64
<success>

Versions

• Operating system: Tumbleweed 20240311 amd64
• Packages: osc-1.6.1-1.1.noarch

Expected behavior

Have the command with the -M notation succeed just as well.

[dmach]

If I remember correctly, multibuild handling is quite inconsistent among commands and use cases.
Let me check if I can change this without losing any consistency.