get allows to retrieve a merge request, to display it. By default it only display "id", "title" and "body" ; verbosity must be augmented to display more.
There is now only "use_pubsub", and specification are set using "pubsub_flags" argument when instantiating CommandBase.
Options are more Python Zen compliant by using explicit arguments for item, draft, url instead of trying to guess with magic keyword and type detection.
Pubsub node and item are now always using respecively "-n" and "-i" even when required, this way shell history can be used to change command more easily, and it's globally less confusing for user.
if --pubsub-url is used, elements can be overwritten with individual option (e.g. change item id with --item).
New "use_draft" argument in CommandBase, to re-use current draft or open a file path as draft.
Item can now be specified when using a draft. If it already exists, its content will be added to current draft (with a separator), to avoid loosing data.
common.BaseEdit.getItemPath could be simplified thanks to those changes.
Pubsub URI handling has been moved to base.py.
