commit-graph: validate layers for generation data

We need to be extra careful that we don't use corrected
commit dates from any layer of a commit-graph chain if there is a
single commit-graph file that is missing the generation_data chunk.
Update validate_mixed_generation_chain() to correctly update each
layer to ignore the generation_data chunk in this case. It now also
returns 1 if all layers have a generation_data chunk. This return
value will be used in the next change.

Signed-off-by: Derrick Stolee <dstolee@microsoft.com>
Reviewed-by: Taylor Blau <me@ttaylorr.com>
Signed-off-by: Junio C Hamano <gitster@pobox.com>

diff --git a/commit-graph.c b/commit-graph.c
index edbb3a0f2cc5d6fac3ed3a1216f019ee44fb18d6..b3f7c3bbcb3a3b1f25966ef00bb3f2125e6a284b 100644 (file)
--- a/commit-graph.c
+++ b/commit-graph.c
@@ -614,19 +614,29 @@ static struct commit_graph *load_commit_graph_chain(struct repository *r,
        return graph_chain;
 }
 
-static void validate_mixed_generation_chain(struct commit_graph *g)
+/*
+ * returns 1 if and only if all graphs in the chain have
+ * corrected commit dates stored in the generation_data chunk.
+ */
+static int validate_mixed_generation_chain(struct commit_graph *g)
 {
-       int read_generation_data;
+       int read_generation_data = 1;
+       struct commit_graph *p = g;
 
-       if (!g)
-               return;
+       while (read_generation_data && p) {
+               read_generation_data = p->read_generation_data;
+               p = p->base_graph;
+       }
 
-       read_generation_data = !!g->chunk_generation_data;
+       if (read_generation_data)
+               return 1;
 
        while (g) {
-               g->read_generation_data = read_generation_data;
+               g->read_generation_data = 0;
                g = g->base_graph;
        }
+
+       return 0;
 }
 
 struct commit_graph *read_commit_graph_one(struct repository *r,