Obsolete Markers and Phases

[Scott Palmer]

On 2012-08-02, at 10:29 AM, Pierre-Yves David <pierre-yves.david at logilab.fr> wrote:

> On Thu, Aug 02, 2012 at 07:26:21AM -0700, v wrote:
>> 
>> Pierre-Yves David wrote
>>> 
>>> On Thu, Aug 02, 2012 at 07:20:53AM -0700, v wrote:
>>>> http://mercurial.selenic.com/wiki/ChangesetsObsolescence and hg help say
>>>> that
>>>> obsolescence can't/shouldn't be used for public changesets.
>>>> 
>>>> Isn't this the whole point?
>>> 
>>> Golden rule:
>>> 
>>>    The whole point of **public** changeset is to be immutable.
>>> 
>> 
>> Does obsolescence mutate changesets?
> 
> Obsolescence marker track changesets mutation.
> 
> Public changeset will refuse to be Mutated.
> 
> Note: Mutation of a changeset is actually the writting a whole new changeset.
>      As per DVCS design.

Can you give us a typical use case?  I'm getting confused by this.  Since the introduction of "public" vs. "private" change sets, I thought rewriting history by actually mutating (or replacing) a changeset was now safe - because it was just a correction or alteration of local data that was not shared yet.

With this concept of obsolescence how does it fit in?  If a changeset is public already is the only case I can think of where it makes sense to use this concept instead of truly rewriting history.  So I'm a bit lost.

Scott