uncommit: set uncommit_source extra consistently in interactive mode Previously, the uncommit_source extra was only explicitly set on the temporary changeset created during the uncommit command. Due to a contract mismatch because the extra() method returned a dict that might be reused for multiple callers and this call site expected a fresh dict, the resulting changeset produced by the uncommit command might or might not have had the correct extra nonetheless. This changeset ensures that it will be set consistently. There is a discussion whether the extra() method (in core) should always return a fresh dict. Independent of the outcome of the discussion, this fix should work. I checked that the tests work no matter whether extra() returns a fresh dict or a reused one (current core behavior).