Unify commands under a single entry point

[0x2b3bfa0]

It would be nice to provide a common cml command to unify all the different scripts that conform our public interface. Executing cml command could be more practical than the current cml-command because the former provides:

• A more sensible default command on our container images, instead of using cml-runner as we're currently doing:
  

  cml/Dockerfile

  Line 104 in 899c6d2

  CMD ["cml-runner"]

• A canonical way of specifying options that are common to all the commands, like obtaining the used CML version. Calling cml-command --version isn't as intuitive as calling cml --version for a set of tools that get released together.

• It would be similar to many other modern command-line tools like gh or dvc where users already expect a single base command.

We can preserve backward compatibility in the same ways as Git, so cml-command and cml command become equivalent.

Additionally, it would be nice to consider more descriptive names for some of the commands and keep aliases for backwards compatibility.

[casperdcl]

btw git already supports subcommands, and gh also just added support. Should do the same for cml.

[skshetry]

btw git already supports subcommands, and gh also just added support. Should do the same for cml.

I have been thinking of doing the same for dvc, but argparse hasn't made that easy. 😄

[DavidGOrtega]

I have been thinking of doing the same for dvc, but argparse hasn't made that easy. 😄

But dvc already have subcommands @skshetry ?

I also thought on this. Will make the code dryer since we also repeat many times variables or prepare the output redirecting the console, etc...

[skshetry]

@DavidGOrtega, yes it does. I was commenting on the link that @casperdcl shared about gh adding support for extension/third-party subcommands. git also supports third-party extension commands already, I am just thinking of ways to do that. 🙂