Re: [BUG] `git describe` doesn't traverse the graph in topological order

> So I finally found some time to go back to this. The actual fix is
> actually rather easy (patch attached). However, as guessed at previously
> in the thread, the performance is in the tank without an up-to-date
> commit graph ("instant" with it versus "minutes" without). On the other
> hand, it is *accurate*. It does fix one expect-fail test case already in
> the test suite (also included in the patch).

> +/*
> + * Topological comparison: always return parents before children.
> + * This is reverse topological order: children before parents.
> + */
> +static int compare_commits_topo(const void *a_, const void *b_, void *_unused_ UNUSED)
> +{
> +	struct commit *a = (struct commit *)a_;
> +	struct commit *b = (struct commit *)b_;
> +	if (repo_is_descendant_of(the_repository, a, &(struct commit_list){ b, NULL }))
> +		return -1; // a is descendant, so comes before b
> +	if (repo_is_descendant_of(the_repository, b, &(struct commit_list){ a, NULL }))
> +		return 1; // b is descendant, so comes before a
> +	// fallback: order by hash for determinism
> +	return oidcmp(&a->object.oid, &b->object.oid);
> +}