Backing out a merge - consequences?

[Becker, Mischa J]

> -----Original Message-----
> From: mercurial-bounces at selenic.com [mailto:mercurial-
> bounces at selenic.com] On Behalf Of Tom Udale
> Sent: Thursday, July 10, 2014 11:41 AM
> To: Matt Mackall
> Cc: mercurial at selenic.com
> Subject: Re: Backing out a merge - consequences?
>
> Hi Matt,
>
> >> We have a situation where a feature branch was inappropriately merged
> >> (and pushed, of course) into the default branch.
> >>
> >> I have on my local machine run
> >>
> >> hg backout -r 1234 --parent 1233
> >>
> >> which has dutifully put my local repo back at the state of rev 1233.
> >
> > The "backing out a merge" behavior was so broken, we deprecated it in
> > 2011. Don't use it.
> >
> > While it has the desired effect on the _contents_ of your changeset,
> > it can't unrecord that a merge happened in your history graph. Since
> > the merge is still there, but with a "null" result, future merges will
> > be confused and dutifully undo the same changes.
>
> I had a feeling something like this was afoot.
>
>
>
> > To fix it, you need to commit a correct merge above the backed-out
> > merge and force all users to update past it so that future merges
> > won't be confused.
>
> This is what I have:
>
>    o           1234 default - "premature merge w\feature"
>    |\
>    o \         1233 default
>    |  \
>    |   o       1232 feature
>    |   |
>
>
> If I understand what you are suggesting, you are saying to do something
> like this:
>
>
> |   o           1236 default - tag "DO NOT Use Me!!"
> o   |           1235 default - tag "Use Me!!"
>  \  |
>   \ o           1234 default - "premature merge w\feature"
>    \|\
>     o \         1233 default
>     |  \
>     |   o       1232 feature
>     |   |
>

It might be better to close the branch after the bad merge so you don't have two heads on default.

 |   =           1236 default - Close branch "Premature merge"
 o   |           1235 default - tag "Use Me!!"
  \  |
   \ o           1234 default - "premature merge w\feature"
    \|\
     o \         1233 default
     |  \
     |   o       1232 feature
     |   |

Mischa

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