Re: 2.29.0.rc0.windows.1: Duplicate commit id error message when fetching

> On 10/8/2020 8:06 AM, Jeff King wrote:
>> But regardless, it seems unfriendly that we can't
>> get out of it while merging the graphs. Doing this obviously makes the
>> problem go away:
>>
>> diff --git a/commit-graph.c b/commit-graph.c
>> index cb042bdba8..ae1f94ccc4 100644
>> --- a/commit-graph.c
>> +++ b/commit-graph.c
>> @@ -2023,8 +2023,11 @@ static void sort_and_scan_merged_commits(struct write_commit_graph_context *ctx)
>>  
>>  		if (i && oideq(&ctx->commits.list[i - 1]->object.oid,
>>  			  &ctx->commits.list[i]->object.oid)) {
>> -			die(_("unexpected duplicate commit id %s"),
>> -			    oid_to_hex(&ctx->commits.list[i]->object.oid));
>> +			/*
>> +			 * quietly ignore duplicates; these could come from
>> +			 * incremental graph files mentioning the same commit.
>> +			 */
>> +			continue;
>>  		} else {
>>  			unsigned int num_parents;
>>  
>>
>> but it's not clear to me if that's papering over another bug, or
>> gracefully handling a situation that we ought to be.
> 
> I think this is a good thing to do, at minimum. As I discussed above,
> the "input data" of the incremental commit-graph chain with duplicate
> commits across layers isn't actually _invalid_. It's unexpected based
> on what Git "should" be doing.