Differentiate defaults from explicitly passed values

[ulope]

Unless I've missed something it seems there is currently no way to differentiate between an explicitly passed value and a default value.

This is problematic for establishing value precedence when dealing with other sources of parameter values (a config file in our case).
We're currently using the default values to detect if a given option was passed on the command line but this is imperfect and leads to the following problem:

• @option('--some-option', default=1)
• Some other way of specifying option values (e.g. a config file) sets some-option = 2
• User calls cli with --some-option 1

Under the above workaround this makes it appear as if the config file value (2) should have precedence even though the user explicitly requested value 1.

[davidism]

How would you propose we distinguish these? I'm not sure if click should even do this, although the info is probably somewhere in the context or could be handled with an extension.