Create a merge commit when pulling/merging changes where all conflicts can be resolved automatically #639

Given: A local branch and remote branch, both with commits. When merging those, all conflicts can be resolved automatically, for example because different files were changed locally and remote.

When such a situation is merged via mergeBranchIntoCurrentBranch (for example as part of pullBranch) in this situation, a merge conflict error will be thrown:
https://github.com/libgit2/objective-git/blob/master/ObjectiveGit/GTRepository+Merging.m#L135

But then the conflicts are written to the index and this index might not have any conflicts because all conflicts were resolved automatically.

In this case, shouldn't the merge commit be created and the operation return without an error?

I tried to solve this, by instead of always returning with an error here: https://github.com/libgit2/objective-git/blob/master/ObjectiveGit/GTRepository+Merging.m#L148
I check if there are actually any remaining conflicts in the index that was written, and if not, I carry on creating the merge commit:

index = [self indexWithError:nil];
if (index.hasConflicts) {
	return NO;
} else {
	*error = nil;
}

This seems to work, not sure if it's the correct solution that covers all cases that can happen in this situation...