diff mbox series

[v2,5/6] commit-graph: be extra careful about mixed generations

Message ID 9bccee8fb6381102d543d6b28e90959307ed08eb.1612234883.git.gitgitgadget@gmail.com (mailing list archive)
State Accepted
Commit fde55b0906552537c8cbcbf654f8e9dd64414637
Headers show
Series Generation Number v2: Fix a tricky split graph bug | expand

Commit Message

Derrick Stolee Feb. 2, 2021, 3:01 a.m. UTC 
From: Derrick Stolee <dstolee@microsoft.com>

When upgrading to a commit-graph with corrected commit dates from
one without, there are a few things that need to be considered.

When computing generation numbers for the new commit-graph file that
expects to add the generation_data chunk with corrected commit
dates, we need to ensure that the 'generation' member of the
commit_graph_data struct is set to zero for these commits.

Unfortunately, the fallback to use topological level for generation
number when corrected commit dates are not available are causing us
harm here: parsing commits notices that read_generation_data is
false and populates 'generation' with the topological level.

The solution is to iterate through the commits, parse the commits
to populate initial values, then reset the generation values to
zero to trigger recalculation. This loop only occurs when the
existing commit-graph data has no corrected commit dates.

While this improves our situation somewhat, we have not completely
solved the issue for correctly computing generation numbers for mixed
layers. That follows in the next change.

Signed-off-by: Derrick Stolee <dstolee@microsoft.com>
---
 commit-graph.c | 14 ++++++++++++--
 1 file changed, 12 insertions(+), 2 deletions(-)
diff mbox series

Patch

diff --git a/commit-graph.c b/commit-graph.c
index 2790f70d113..ee8d5a0cdb4 100644
--- a/commit-graph.c
+++ b/commit-graph.c
@@ -1036,7 +1036,8 @@  struct write_commit_graph_context {
 		 split:1,
 		 changed_paths:1,
 		 order_by_pack:1,
-		 write_generation_data:1;
+		 write_generation_data:1,
+		 trust_generation_numbers:1;
 
 	struct topo_level_slab *topo_levels;
 	const struct commit_graph_opts *opts;
@@ -1508,6 +1509,15 @@  static void compute_generation_numbers(struct write_commit_graph_context *ctx)
 		ctx->progress = start_delayed_progress(
 					_("Computing commit graph generation numbers"),
 					ctx->commits.nr);
+
+	if (!ctx->trust_generation_numbers) {
+		for (i = 0; i < ctx->commits.nr; i++) {
+			struct commit *c = ctx->commits.list[i];
+			repo_parse_commit(ctx->r, c);
+			commit_graph_data_at(c)->generation = GENERATION_NUMBER_ZERO;
+		}
+	}
+
 	for (i = 0; i < ctx->commits.nr; i++) {
 		struct commit *c = ctx->commits.list[i];
 		timestamp_t corrected_commit_date;
@@ -2439,7 +2449,7 @@  int write_commit_graph(struct object_directory *odb,
 	} else
 		ctx->num_commit_graphs_after = 1;
 
-	validate_mixed_generation_chain(ctx->r->objects->commit_graph);
+	ctx->trust_generation_numbers = validate_mixed_generation_chain(ctx->r->objects->commit_graph);
 
 	compute_topological_levels(ctx);
 	if (ctx->write_generation_data)