[PATCH] merge: warn about adding unstable commit

[timeless]

Pierre-Yves David wrote:
> Not really enthusiastic.

> What happen here is that you have an obsolete
> working copy parent and that will lead to unstable changeset on commit.

Correct

> We -already- have a message for obsolete working copy parent.
> It live in the evolve extensions.

something parent related:
        ui.warn(_('working directory parent is obsolete!\n'))
        if (not ui.quiet) and obsolete.isenabled(repo, commandopt):
            ui.warn(_('(use "hg evolve" to update to its successor)\n'))

something generic:
        ui.warn(_('%i new unstable changesets\n') % newunstables)

These are the only messages I could find. They aren't very helpful.

> (used by various command including hg update` and `hg pull`)

Pulls are things which can happen automatically in unrelated actions.
I certainly don't pay attention to them.

> We should:
>
> 1) Use the same message in both case,

I'm +0..-1/2 on this. I'm not sure what the message in evolve says (I
looked and found the two I mentioned above), but if it says "+2000
unstable", that's absolutely not a helpful message.

Messages need to be *relevant* to the current action, if they're
unrelated/irrelevant, they aren't helpful, and might as well be noise
(and thus would be better served by being omitted).

> 2) improve that unified message if we think we should,

I'm leaning toward -1/2 on "unified".
I'm +1 on trying to improve the evolve ux, although not this year
(i.e. 2015), and I'd really request someone set up a pushgate.

> 3) (probably) move this message from evolve into code now that we have a
> clearer policy about "This is experimental stuff in Core, we can change it
> until we lift the experimental adjective to t

The terminology bothers me a bunch of ways.
But, I can definitely have obsolete markers from histedit/rebase +
exchange, so an out of core thing is definitely the wrong place for
them.

> Let me know if my feedback is clear enough.

Your feedback is clear.

FWIW, an alternative to setting up a pushgate is just to move evolve
into core's hgext with a big warning saying that it is going to change
a lot. I'm not sure how we feel about that (if anyone wants to reply
on this point, please create a new thread).