pointer to store the index result in
repository that contains the given trees
the common ancestor between the trees (or null if none)
the tree that reflects the destination tree
the tree to merge in to our_tree
the merge tree options (or null for defaults)
0 on success or error code
Merge two trees, producing a git_index that reflects the result of the merge. The index may be written as-is to the working directory or checked out. If the index is to be converted to a tree, the caller should resolve any conflicts that arose as part of the merge.
The returned index must be freed explicitly with git_index_free.