Property separator not appended after argument value if argument completer uses non-zero offset

For example:
module add --name=foo --dependencies=sun.scripting ==> space character is added at the end.
module add --name=foo --dependencies=sun.scripting,sun.jdk ==> Nothing happens, no space character added.
deployment-overlay add --name=foo --contents=foo=/some/file<TAB> ==> Nothing happens, no space character added.

This seems to be caused by a condition in OperationRequestCompleter - if a suggested value is the same as current user input, ORC replaces the suggestion with a separator.
This only works if the offset returned by argument completer is 0 - if the completer provides only part of the value, this condition will never be triggered.