commit-graph: prefer default size_mult when given zero

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.

Signed-off-by: Derrick Stolee <dstolee@microsoft.com>
Signed-off-by: Junio C Hamano <gitster@pobox.com>

diff --git a/builtin/fetch.c b/builtin/fetch.c
index 863c858fde9afb3daac09c7ecf83cf44834574d5..0c15f347af2b9fce453e16aa88f0e4fb0195a994 100644 (file)
--- a/builtin/fetch.c
+++ b/builtin/fetch.c
@@ -1867,15 +1867,13 @@ int cmd_fetch(int argc, const char **argv, const char *prefix)
        prepare_repo_settings(the_repository);
        if (the_repository->settings.fetch_write_commit_graph) {
                int commit_graph_flags = COMMIT_GRAPH_WRITE_SPLIT;
-               struct split_commit_graph_opts split_opts;
-               memset(&split_opts, 0, sizeof(struct split_commit_graph_opts));
 
                if (progress)
                        commit_graph_flags |= COMMIT_GRAPH_WRITE_PROGRESS;
 
                write_commit_graph_reachable(get_object_directory(),
                                             commit_graph_flags,
-                                            &split_opts);
+                                            NULL);
        }
 
        close_object_store(the_repository->objects);

diff --git a/commit-graph.c b/commit-graph.c
index 0aea7b2ae5263899b2b93e5acbcd1f391814e0f3..baa1a266b429caa81a0699c5c03aa9e050452d6f 100644 (file)
--- a/commit-graph.c
+++ b/commit-graph.c
@@ -1545,7 +1545,9 @@ static void split_graph_merge_strategy(struct write_commit_graph_context *ctx)
 
        if (ctx->split_opts) {
                max_commits = ctx->split_opts->max_commits;
-               size_mult = ctx->split_opts->size_multiple;
+
+               if (ctx->split_opts->size_multiple)
+                       size_mult = ctx->split_opts->size_multiple;
        }
 
        g = ctx->r->objects->commit_graph;