[PATCH v4 01/10] commit-graph: fix regression when computing Bloom filters

From: Abhishek Kumar <redacted>

commit_gen_cmp is used when writing a commit-graph to sort commits in
generation order before computing Bloom filters. Since c49c82aa (commit:
move members graph_pos, generation to a slab, 2020-06-17) made it so
that 'commit_graph_generation()' returns 'GENERATION_NUMBER_INFINITY'
during writing, we cannot call it within this function. Instead, access
the generation number directly through the slab (i.e., by calling
'commit_graph_data_at(c)->generation') in order to access it while
writing.

While measuring performance with `git commit-graph write --reachable
--changed-paths` on the linux repository led to around 1m40s for both
HEAD and master (and could be due to fault in my measurements), it is
still the "right" thing to do.

Signed-off-by: Abhishek Kumar <redacted>
---
 commit-graph.c | 4 ++--
 1 file changed, 2 insertions(+), 2 deletions(-)

diff --git a/commit-graph.c b/commit-graph.c
index cb042bdba8..94503e584b 100644
--- a/commit-graph.c
+++ b/commit-graph.c

@@ -144,8 +144,8 @@ static int commit_gen_cmp(const void *va, const void *vb)
 	const struct commit *a = *(const struct commit **)va;
 	const struct commit *b = *(const struct commit **)vb;
 
-	uint32_t generation_a = commit_graph_generation(a);
-	uint32_t generation_b = commit_graph_generation(b);
+	uint32_t generation_a = commit_graph_data_at(a)->generation;
+	uint32_t generation_b = commit_graph_data_at(b)->generation;
 	/* lower generation commits first */
 	if (generation_a < generation_b)
 		return -1;

-- 
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