Make path argument in all CLI commands optional using Argument callback

[rominf]

quetz start allows to omit path argument and fallbacks to the current directory:

quetz/quetz/cli.py

Lines 538 to 542 in a189de8

	if path:
	deployment_folder = Path(path)
	else:
	deployment_folder = Path("")
	path = os.getcwd()

However it's not the case for other commands. For example, quetz make-migrations without path fails with the exception:

TypeError: expected str, bytes or os.PathLike object, not NoneType

This is partially fixed by: #644 (because of proper annotations error message is more appropriate), but still, this is not consistent, and it could be more user-friendly.

I propose to make path argument in all CLI commands optional by using Argument callback for updating the value of path to current directory and validating it using _is_deployment function.

• I am ready to create a PR.

[wolfv]

This sounds very reasonable, too. Sorry that it took so long to get back to you.