Separate help texts for subcommands that are internally implemented as aliases

[smithfarm]

Is your feature request related to a problem? Please describe.

When users issue --help for an osc subcommand that is internally implemented as an alias, they get a wall of text, most of which might seem completely unrelated to the osc subcommand they are interested in. Users are forced to sift through this text to find the bits that relate to the subcommand for which they asked for help.

Describe the solution you'd like

The output of osc foo --help should only pertain to foo, and not to any other subcommands, even if foo is internally implemented as an alias.

Describe alternatives you've considered

None.

Additional context

A classic example is the help text displayed when the user issues the command osc shell --help. Since shell is internally an alias of build, the users get the whole help text for build and are forced to read through all of it to find the shell bits they are interested in.

[dmach]

This requires massive refactoring of the commands.
Keeping in backlog as a reminder, because we definitely want osc to move in this direction.