Re: commit-graph idea: warn when disabled for incompatible repositories

[Derrick Stolee <stolee@gmail.com>]

On 12/18/2018 1:21 PM, Ævar Arnfjörð Bjarmason wrote:
> diff --git a/builtin/gc.c b/builtin/gc.c
> index 871a56f1c5..702568b70d 100644
> --- a/builtin/gc.c
> +++ b/builtin/gc.c
> @@ -662,9 +662,14 @@ int cmd_gc(int argc, const char **argv, const char *prefix)
>   	if (pack_garbage.nr > 0)
>   		clean_pack_garbage();
>
> -	if (gc_write_commit_graph)
> +	if (gc_write_commit_graph) {
> +		int verbose = !quiet && !daemonized;
> +		if (verbose && !commit_graph_compatible(the_repository))
> +			warning(_("The `gc.writeCommitGraph' setting is on, "
> +				  "but commit_graph_compatible() = false"));
>   		write_commit_graph_reachable(get_object_directory(), 0,
> -					     !quiet && !daemonized);
> +					     verbose);
> +	}

I actually think this is the wrong place to put it. This will cause a 
warning for someone with 'gc.writeCommitGraph' enabled and running GC on 
a shallow clone.

I think the issue was someone running 'git commit-graph write' inside a 
shallow clone that succeeds without doing anything.

Also, I bet you would hit this block if you run the test suite with 
GIT_TEST_COMMIT_GRAPH=1.

Thanks,

-Stolee


>   	if (auto_gc && too_many_loose_objects())
>   		warning(_("There are too many unreachable loose objects; "
> diff --git a/commit-graph.c b/commit-graph.c
> index 40c855f185..60915bf9aa 100644
> --- a/commit-graph.c
> +++ b/commit-graph.c
> @@ -61,7 +61,7 @@ static struct commit_graph *alloc_commit_graph(void)
>
>   extern int read_replace_refs;
>
> -static int commit_graph_compatible(struct repository *r)
> +int commit_graph_compatible(struct repository *r)
>   {
>   	if (!r->gitdir)
>   		return 0;
> diff --git a/commit-graph.h b/commit-graph.h
> index 9db40b4d3a..7c92d41a28 100644
> --- a/commit-graph.h
> +++ b/commit-graph.h
> @@ -12,6 +12,8 @@ struct commit;
>
>   char *get_commit_graph_filename(const char *obj_dir);
>
> +int commit_graph_compatible(struct repository *r);
> +
>   /*
>    * Given a commit struct, try to fill the commit struct info, including:
>    *  1. tree object

This part looks correct, and necessary for the warning in 
builtin/commit-graph.c

Thanks,

-Stolee