Re: [PATCH 1/1] commit-graph.c: avoid unnecessary tag dereference when merging

> On Sat, Mar 21, 2020 at 08:03:01PM -0400, Derrick Stolee wrote:
>> On 3/21/2020 2:50 PM, Junio C Hamano wrote:
>>> Do we need to worry about INFO_QUICK and SKIP_FETCH_OBJECT in this
>>> codepath, by the way?
>>
>> I was coming back to this thread to bring up these exact flags for
>> consideration. The good news is that in a partial clone with any
>> amount of filtering we will still have all reachable commits, which
>> are necessary for the commit-graph to make sense. The only ones that
>> would fail has_object_file() are ones removed by GC, but they may
>> still exist on the remote. So without SKIP_FETCH_OBJECT, we would
>> generate a network call even if the server has GC'd to remove the
>> commits. This gets particularly bad when the server returns all
>> reachable objects from that commit!
> 
> That makes sense. Do you think something like this should be applied?

> diff --git a/commit-graph.c b/commit-graph.c
> index c7cfadc786..0097318798 100644
> --- a/commit-graph.c
> +++ b/commit-graph.c
> @@ -1594,6 +1594,7 @@ static void merge_commit_graph(struct write_commit_graph_context *ctx,
>  {
>         uint32_t i;
>         uint32_t offset = g->num_commits_in_base;
> +       int flags = OBJECT_INFO_QUICK | OBJECT_INFO_SKIP_FETCH_OBJECT;
> 
>         ALLOC_GROW(ctx->commits.list, ctx->commits.nr + g->num_commits, ctx->commits.alloc);
> 
> @@ -1606,7 +1607,7 @@ static void merge_commit_graph(struct write_commit_graph_context *ctx,
>                 load_oid_from_graph(g, i + offset, &oid);
> 
>                 /* only add commits if they still exist in the repo */
> -               if (repo_has_object_file(ctx->r, &oid)) {
> +               if (repo_has_object_file_with_flags(ctx->r, &oid, flags)) {
>                         result = lookup_commit(ctx->r, &oid);
>                         if (repo_parse_commit(ctx->r, result))
>                                 result = NULL;