Re: [PATCH 09/10] name-rev: generate name strings only if they are better

[Derrick Stolee <stolee@gmail.com>]

On 2/4/2020 4:25 PM, René Scharfe wrote:
> -			if (create_or_update_name(parent, new_name, taggerdate,
> -						  generation, distance,
> -						  from_tag)) {
> +			parent_name = create_or_update_name(parent, taggerdate,
> +							    generation,
> +							    distance, from_tag);
> +			if (parent_name) {

As someone unfamiliar with the name-rev code, it took me a while to see why
the algorithm isn't exponential in complexity. It technically _is_, but it
is of the form 2^{N / MERGE_TRAVERSAL_WEIGHT} = 2^{N / 65535} and only if
we create a particularly nasty commit history that would never appear in the wild.

But, the critical section is the block above. The confusing part was that
create_or_update_name() returns NULL if the name is updated, but non-NULL if
a better name is created. That makes it clear that this change is saving
allocations.

Thanks,
-Stolee