Where do all the tips go? (Was: Re: Sharing a massive distributed merge)

> On Thu, Mar 17, 2011 at 01:21:19AM -0400, Jay Soffian wrote:
> 
>>> Git doesn't support distribution of a merge (although that would be
>>> extraordinarily cool), so the next best thing seemed to be force adding all
>>> files with conflict markers and then committing the merge.  We then publish
>>> the conflicting branch and have each person fix their files.  Given that the
>>> conflict markers are already in place, they can't use their favorite
>>> graphical merge tool.
>>
>> Well, this is awful, but you could do something like:
>>
>> for x in conflicted_files:
>>    git show :1:$x > $x.base
>>    git show :3:$x > $x.theirs
>>    git checkout --ours $x
>>    git add $x.base $x.theirs $x
>>
>> Commit that, then folks can use their favorite merge tools, commit the
>> result, and remove the .base and .theirs.
> 
> I don't think you need to do anything so drastic. You can just have
> everybody do the partial merge, commit, and then push their result.  And
> then as you suggest below, one person does the real merge, uses checkout
> to install the desired result state from each person's partial tree, and
> then everybody throws away their partial merges.
> 
> The trick is that each person will resolve some conflicts and commit,
> but you need to know which ones they resolved. They can't leave things
> unmerged in the final commit. So they would have to provide such a list
> to you; one way is in the commit message[1].
> 
> So let's say you have three devs, Alice, Bob, and Charlie, and one
> integrator, Matt, who will do the merge. Each of the developers does:
> 
>   git checkout -b partial-merge
>   git merge old-topic
>   git mergetool ;# or manually resolve and git add
> 
> Eventually they get tired of the conflicts and give up. So they record
> the list of resolved paths, either manually or with something like[2]:
> 
>   {
>     echo 'partial merge result'
>     echo
> 
>     git status --porcelain | perl -ne '
>       next if /^U|\?/;
>       s/^\S+\s+//;
>       print;
>     '
> 
>   } >msg
> 
> And then they stage the rest of it (knowing it will be ignored by Matt)
> and commit:
> 
>   git add -u
>   git commit -F msg
>   git push wherever partial-merge
> 
> Then Matt does the actual merge:
> 
>   git merge old-topic
> 
> which of course results in lots of conflicts. So he pulls resolved
> versions from each person's tree:
> 
>   for i in alice bob charlie; do
>     git fetch $i
>     git checkout $i/partial-merge -- \
>       `git log -1 --format:%b $i/partial-merge`
>   done
> 
> And then fixes up whatever's left manually or with git-mergetool, and
> commits the end result.
> 
> Take all of my scripting there as illustrative of the concept, but not
> necessarily a good idea. In particular, it doesn't handle quoting of
> filenames at all, and it probably doesn't handle files whose resolution
> was to be deleted (since the checkout will fail).