On Thu, Jan 02, 2020 at 04:14:14PM +0000, Derrick Stolee via GitGitGadget wrote:
> From: Derrick Stolee <dstolee@xxxxxxxxxxxxx>
>
> In 50f26bd ("fetch: add fetch.writeCommitGraph config setting",
> 2019-09-02), the fetch builtin added the capability to write a
> commit-graph using the "--split" feature. This feature creates
> multiple commit-graph files, and those can merge based on a set
> of "split options" including a size multiple. The default size
> multiple is 2, which intends to provide a log_2 N depth of the
> commit-graph chain where N is the number of commits.
>
> However, I noticed during dogfooding that my commit-graph chains
> were becoming quite large when left only to builds by 'git fetch'.
> It turns out that in split_graph_merge_strategy(), we default the
> size_mult variable to 2 except we override it with the context's
> split_opts if they exist. In builtin/fetch.c, we create such a
> split_opts, but do not populate it with values.
>
> This problem is due to two failures:
>
> 1. It is unclear that we can add the flag COMMIT_GRAPH_WRITE_SPLIT
> with a NULL split_opts.
> 2. If we have a non-NULL split_opts, then we override the default
> values even if a zero value is given.
>
> Correct both of these issues. First, do not override size_mult when
> the options provide a zero value. Second, stop creating a split_opts
> in the fetch builtin.
Thanks, the explanation and fix (both parts) look good to me, modulo the
subject correction you already noted.
> ---
> builtin/fetch.c | 4 +---
> commit-graph.c | 4 +++-
Is it worth covering this with a test?
I guess the non-fetch code paths for splitting already cover this pretty
well, and this is just about managing to get the right number into the
commit-graph code. So perhaps it isn't worth it.
-Peff
