`dotnet <cmd>` without argument doesn't display help text

[ZeroErrors]

Executing commands such as any of

• dotnet sln
• dotnet add
• dotnet remove
• dotnet list
• dotnet sdk
• dotnet workload

Will simply print the following message without displaying the help text.

Required command was not provided.

I tested this on both main (2c011f2) and the latest preview release 6.0.100-preview.5.21302.13 and both have this same problem.

.NET SDK (reflecting any global.json):
 Version:   6.0.100-preview.5.21302.13
 Commit:    d6380bcae7

This bug is a regression of:

• dotnet <cmd> Show help info when no or wrong arguments are given cli#6506
• dotnet add 'dotnet add' with no arguments should probably show output of dotnet add --help #7558
• dotnet sln 'dotnet sln' with no arguments should probably show output of dotnet sln --help #7559
• dotnet sln Not intuitive error message when missing argument (i.e. dotnet sln) #7775

I couldn't figure out the best area label to add to this issue. If you have write-permissions please help me learn by adding exactly one area label.

[marcpopMSFT]

@sfoslund , this is a change of behavior from 5.0 SDKs and appears to be related to the the system commandline adoption