-S or --supported is informative only and should show the supported matrix regardless of other arguments for specific command, eg.:
$ mbed export -S
usage: mbed export [-h] -i IDE [-m TARGET] [--source SOURCE] [-c] [-S] [-v]
[-vv]
mbed export: error: argument -i/--ide is required
If I specify any IDE it fails other way:
$ mbed export -i GCC_ARM -S
[mbed] WARNING: Could not find mbed program in current path "/home/jazg/tmp".
[mbed] WARNING: You can fix this by calling "mbed new ." or "mbed config root ." in the root of your program.
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[mbed] ERROR: The mbed tools were not found in "/home/jazg/tmp".
[mbed] ERROR: Run `mbed deploy` to install dependencies and tools.
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I only wanted to see supported matrix. Ideally such informative operations should go to separate command that do not require any other arguments, say mbed info (like for example docker info).