commit-graph: prefer default size_mult when given zero

derrickstolee · gitster · commit 63020f175fe2 · 2020-01-02T13:46:34.000-08:00
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
@@ -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
@@ -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;

Original file line number	Diff line number	Diff line change
`@@ -1545,7 +1545,9 @@ static void split_graph_merge_strategy(struct write_commit_graph_context *ctx)`
`1545`	`1545`
`1546`	`1546`	`if (ctx->split_opts) {`
`1547`	`1547`	`max_commits = ctx->split_opts->max_commits;`
`1548`		`- size_mult = ctx->split_opts->size_multiple;`
	`1548`	`+`
	`1549`	`+ if (ctx->split_opts->size_multiple)`
	`1550`	`+ size_mult = ctx->split_opts->size_multiple;`
`1549`	`1551`	`}`
`1550`	`1552`
`1551`	`1553`	`g = ctx->r->objects->commit_graph;`