config: add note

The core purpose of `Prepare_config()` is to prepare the config by setting
defaults where not specified. It should not be involved itself in
validation of user options.

This can be an important distinction, for instance in `clean` where we
use this function, but avoid validation to potentially allow for an option
that deletes the config, that should work even in the face of an invalid
config.

Gbp-Dch: Ignore

functions/configuration.sh

@@ -10,6 +10,9 @@
 
 
 # Prepare config for use, filling in defaults where no value provided for instance
+#
+# This function should avoid performing validation checks and failing from invalid values.
+# Validation should be done through `Validate_config()`.
 Prepare_config ()
 {
 	# Colouring is re-evaluated here just incase a hard coded override was given in the saved config