When using a custom template you can use variables like {clean} which are not enabled by default. This causes an ugly traceback.
This fixes the issue by implying --all when --custom (or more exactly --template) is used, so that all variables are available in templates.
This was the easier fix than having the template code report that the user should pass --check-clean to have {clean} available, but will have a performance impact on all users of version-info --custom, regardless of whether they use {clean}.