[PATCH] backout: add example of backing out a merge changeset

[Matt Mackall]

On Wed, 2015-09-30 at 08:51 +0200, Mathias De Maré wrote:
> On Wed, Sep 30, 2015 at 8:29 AM, Pierre-Yves David <
> pierre-yves.david at ens-lyon.org> wrote:
> 
> >
> >
> > On 09/29/2015 10:35 PM, Mathias De Maré wrote:
> >
> >> # HG changeset patch
> >> # User Mathias De Maré <mathias.demare at gmail.com>
> >> # Date 1443590812 -7200
> >> #      Wed Sep 30 07:26:52 2015 +0200
> >> # Node ID 5a00a9ab705848b7de45b4263ed0bbab29494e29
> >> # Parent  46af0adb5c375cc51ce0d29cbdcd8ba843a33425
> >> backout: add example of backing out a merge changeset
> >>
> >
> > How does this cope with:
> >
> >     Note:
> >       backout cannot be used to fix either an unwanted or incorrect merge.
> >
> > Did you read previous discussion on the topic?
> 
> I found the following about the topic:
> https://selenic.com/pipermail/mercurial-devel/2011-October/034559.html
> The issues described are when you have 2 valid branches and the merge
> between them goes wrong.
> But what I describe here is when one of the branches is bad (and all the
> changes on it are bad), while the other branch is good.
> In that case, I would like to apply the inverse of the branch, and it seems
> to be like that would indeed solve my issue.
> 
> Matt describes here (see the last example) the issue of backing out an
> entire merge:
> https://selenic.com/pipermail/mercurial-devel/2011-October/034569.html
> 
> > In other words, you just turned a broken real merge into a dummy merge,
> > which is probably not what you wanted.
> >
> > In fact, that is what I wanted. I agree that a backout of a merge is a
> broken concept in some of the cases, but I believe it is a valid concept
> for the case I'm describing.
> Perhaps I'm missing something here?

We don't want to even mention merge in the backout docs because people
will try to do something it can't really do and compound the damage on
their DAG.

It's pretty easy to just use revert to make a dummy merge, no?

-- 
Mathematics is the supreme nostalgia of our time.