Re: [RFC PATCH 4/6] commit-graph: avoid writing when repo is shallow

[Derrick Stolee <stolee@gmail.com>]

On 5/31/2018 10:30 PM, Junio C Hamano wrote:
> Derrick Stolee <dstolee@microsoft.com> writes:
>
>> Shallow clones do not interact well with the commit-graph feature for
>> several reasons. Instead of doing the hard thing to fix those
>> interactions, instead prevent reading or writing a commit-graph file for
>> shallow repositories.
> The latter instead would want to vanish, I would guess.

Do you mean that we should call destroy_commit_graph() if we detect a 
shallow repository during write_commit_graph(), then I can make that change.

>
>> Signed-off-by: Derrick Stolee <dstolee@microsoft.com>
>> ---
>>   commit-graph.c | 12 ++++++++++++
>>   1 file changed, 12 insertions(+)
>>
>> diff --git a/commit-graph.c b/commit-graph.c
>> index 95af4ed519..80e377b90f 100644
>> --- a/commit-graph.c
>> +++ b/commit-graph.c
>> @@ -208,6 +208,9 @@ static void prepare_commit_graph(void)
>>   		return;
>>   	prepare_commit_graph_run_once = 1;
>>   
>> +	if (is_repository_shallow())
>> +		return;
>> +
>>   	obj_dir = get_object_directory();
>>   	prepare_commit_graph_one(obj_dir);
>>   	prepare_alt_odb();
>> @@ -711,6 +714,15 @@ void write_commit_graph(const char *obj_dir,
>>   	int num_extra_edges;
>>   	struct commit_list *parent;
>>   
>> +	/*
>> +	 * Shallow clones are not supproted, as they create bad
>> +	 * generation skips as they are un-shallowed.
>> +	 */
>> +	if (is_repository_shallow()) {
>> +		warning("writing a commit-graph in a shallow repository is not supported");
>> +		return;
>> +	}
>> +
>>   	oids.nr = 0;
>>   	oids.alloc = approximate_object_count() / 4;