On Mon, Sep 17, 2018 at 6:25 PM Junio C Hamano <gitster@xxxxxxxxx> wrote: > > Nguyễn Thái Ngọc Duy <pclouds@xxxxxxxxx> writes: > > > This function calls do_diff_cache() which eventually needs to set this > > "istate" to unpack_options->src_index (*). This is an unfortunate fact > > that unpack_trees() _will_ destroy src_index so we can't really pass a > > Wasn't the whole point of introducing src_index and dst_index to > unpack-trees API so that we can keep the src_index read-only by > writing the result of merge to a separate in-core dst_index? > > What does the above exactly mean by "will destroy src_index"? Is it > now fundamental that src_index needs to lack constness, or is it > something easy to fix? "destroy" is probably a strong word, but we do modify the src_index, e.g. mark_all_ce_unused(o->src_index); mark_new_skip_worktree(.., o->src_index... move_index_extensions(&o->result, o->src_index); invalidate_ce_path(); all these update the source index. It is possible to fix, but I don't think it's exactly easy and may even incur some performance cost (e.g. if we stop modify ce_flags in the src_index, then we need to do one extra lookup to wherever we store these flags). -- Duy
