The change is quite new and undocumented (since it is experimental) so it seems
premature to make it available in tweak default. In addition, I am not sure the
new return code are frozen yet (eg: some of the initial feedback have not been
incorporated). Before the release I doubled check (probably with Martin) that
they were not enabled by default and got replied that they were only enabled in
the tests. Have I been aware that they have been also enabled in tweak default I
would I have lobbied to delay that.
I discovered they were in tweak default from users feedback. They found it an
unpleasant and unexpected surprise of 5.7.
So I suggest we no enable enable this experimental feature for Mercurial 5.7 and
revisit this later, when the feature will be more mature.