pointer to store the index result in
the repository that contains the given commits
the commit to revert
the commit to revert against (eg, HEAD)
the parent of the revert commit, if it is a merge
the merge options (or null for defaults)
zero on success, -1 on failure.
Reverts the given commit against the given "our" commit, producing an index that reflects the result of the revert.
The returned index must be freed explicitly with git_index_free.