Merge file favor options for git_merge_options instruct the file-level
merging functionality how to deal with conflicting regions of the files.
When a region of a file is changed in both branches, a conflict will be recorded in the index so that git_checkout can produce a merge file with conflict markers in the working directory. This is the default.
When a region of a file is changed in both branches, the file created in the index will contain the "ours" side of any conflicting region. The index will not record a conflict.
When a region of a file is changed in both branches, the file created in the index will contain the "theirs" side of any conflicting region. The index will not record a conflict.
When a region of a file is changed in both branches, the file created in the index will contain each unique line from each side, which has the result of combining both files. The index will not record a conflict.