Add metaflow-diff to main CLI

[npow]

Had to shorten the help text to prevent it being chopped off:

metaflow help

Usage: metaflow [OPTIONS] COMMAND [ARGS]...

Options:
  --help  Show this message and exit.

Commands:
  admin        Execute admin commands.
  code         Metaflow code commands
  debug        Post/Pre Step debugging commands
  develop      Metaflow develop commands
  environment  Execution environment related commands.
  help         Show all available commands.
  status       Show flows accessible from the current working tree.
  tutorials    Browse and access the metaflow tutorial episodes.
  workbench    Workbench related commands

metaflow code --help

Usage: metaflow code [OPTIONS] COMMAND [ARGS]...

  Metaflow code commands

Options:
  --help  Show this message and exit.

Commands:
  diff       Do a 'git diff' of the current directory and a Metaflow run.
  diff-runs  Do a 'git diff' between two Metaflow runs.
  patch      Create a patch file for the current dir with a Metaflow run.
  pull       Pull the code of a Metaflow run.

[romain-intel]

echo and echo_always are a bit confusing here (one calls the other with some foreground, etc). Also, not sure if we want to respect the quiet flag?

[npow]

what is your suggestion? get rid of echo?

[romain-intel]

Some comments.

[romain-intel]

why one and the other? THey seem to do the same?

[npow]

not sure. @tuulos ^

[tuulos]

sorry, what's the question @romain-intel ?

[npow]

Superseded by #2282