Feature enable common ancestors (diff3)

ghost commented 4 years ago

What's this PR?

This pr changes as it can recognize common ancestors part.

When merge.conflictstyle = diff3 is set, git shows common ancestors with mark |||||||.

Right now, conflict-marker.vim recognizes it as ours part.

If you command ConflictMarkerOurselves, common ancestors remains. It's not as expected.

Therefore, I make it be able to recognize common ancestors part. This's compatible with merge.conflictstyle = default.

I checked ConflictMarkNone, ConflictMarkBoth, ConflictMarkTheirs, and ConflictOurs when merge.conflictstyle is default or diff3. All works as expected.
I don't put common_ancestors search in autoload/conflict_marker/detect.vim, because common_ancestors doesn't exist when merge.conflictstyle is not diff3. Also, it's not required to check since begin, separate, and end are enough.

ghost commented 4 years ago

I now realize there is an issue about this.

ghost commented 4 years ago

@rhysd Thank you for reviewing. I fixed two things you pointed out.