Re: [PATCH] merge-tree: load default git config

[Derrick Stolee <derrickstolee@github.com>]

On 5/10/2023 4:30 PM, Felipe Contreras wrote:
> Derrick Stolee via GitGitGadget wrote:
>> From: Derrick Stolee <derrickstolee@github.com>
>>
>> The 'git merge-tree' command handles creating root trees for merges
>> without using the worktree. This is a critical operation in many Git
>> hosts, as they typically store bare repositories.
>>
>> This builtin does not load the default Git config, which can have
>> several important ramifications.
> 
> For the record, I had already sent a better version of this patch almost 2
> years ago [1], not just for `git merge-tree`, but other commands as well.
> 
> The obvious fix was completely ignored by the maintainer.
> 
> The reason why it should be git_xmerge_config and not git_default_config, is
> that merge.conflictstyle would not be parsed if you call git_default_config.

As mentioned by Elijah in a different thread, the merge machinery loads
the merge config as needed. I confirmed by creating this test, which I
may submit as an independent patch:

test_expect_success 'merge-tree respects merge.conflictstyle' '
	test_commit conflict-base &&
	for branch in left right
	do
		git checkout -b $branch conflict-base &&
		echo $branch >>conflict-base.t &&
		git add conflict-base.t &&
		git commit -m $branch || return 1
	done &&

	test_must_fail git merge-tree left right >out1 &&
	test_must_fail git -c merge.conflictstyle=diff3 merge-tree left right >out2 &&

	tree1=$(head -n 1 out1) &&
	tree2=$(head -n 1 out2) &&

	git cat-file -p $tree1:conflict-base.t >conflict1 &&
	git cat-file -p $tree2:conflict-base.t >conflict2 &&
	! test_cmp conflict1 conflict2 &&
	! grep "||||||" conflict1 &&
	grep "||||||" conflict2
'

Thus we do not need to use git_xmerge_config at this point in the
process.

Thanks,
-Stolee