Re: merge summaries

From: Steffen Prohaska <prohaska@zib.de>
Date: May 19, 2007, 09:35 UTC
Message-ID: <73A1C4C5-50E9-4844-85F8-00D99682B6D4@zib.de>
In-Reply-To: <7vodki55px.fsf@assigned-by-dhcp.cox.net>

On May 18, 2007, at 8:47 PM, Junio C Hamano wrote:

Show 22 quoted lines

>> Think about _who_ uses it for those two prominent repositories for  
>> a while.
>>
>> [ pause, ponder here ]
>>
>> In other words, "merge.summary" should be true ONLY FOR TOP-LEVEL
>> MAINTAINERS.
>>
>> Making it true for anybody else is almost always a bug. Yes, I and  
>> Junio
>> have it enabled, but pretty much nobody else should, because if  
>> they pull
>> from me or Junio in order to merge, their merge summaries would be  
>> exactly
>> the wrong way around!
>
> This does not necessarily mean that your lieutenants should not
> use merge.summary when they pull from other trees (or inside
> their own repository to merge in the topics).  They need to
> however disable it with --no-summary when they pull from you
> when they choose to merge instead of rebase to adjust to the
> updated infrastructure in your tree.

[ ... pondering ... ]

Apparently parents of merge commits are not fully equal and summaries can help to browse the history of a branch. If summaries are enabled "git log --first-parent" gives hints to all changes at least in short-log form. Changes along the first-parent-path to the initial commit are listed in full. All changes that were merged in are listed in the summaries of the merge. This seems to be a useful feature.

But isn't this true for any branch and any merge. If someone pulls from you or Junio and runs "git log --first-parent" why shouldn't he see a summary of the changes that were pulled? At that point his branch's first-parent-path to the initial commit would not touch the changes pulled from you. So the summary could help.

What is so wrong if merge summaries of pulls from you were committed to topic branches. Later when you pull such branches the summaries shouldn't be a problem. A short-log of the topic branch wouldn't contain the summaries.

Probably I do not fully understand what "the wrong way around" means.

- Steffen