[PATCH v4 4/9] commit-graph: simplify compute_generation_numbers()

["Derrick Stolee via GitGitGadget" <gitgitgadget@gmail.com>]

From: Derrick Stolee <derrickstolee@github.com>

The previous change introduced the generic algorithm
compute_reachable_generation_numbers() and used it as the core
functionality of compute_topological_levels(). Now, use it as the core
functionality of compute_generation_numbers().

The main difference here is that we use generation version 2, which is
used in to toggle the logic in compute_generation_from_max() for
computing the corrected commit date based on the corrected commit dates
of the parent commits (and the commit date of the current commit). It
also uses different methods for (get|set)_generation in the vtable in
order to store and access the value in the correct places.

Co-authored-by: Taylor Blau <me@ttaylorr.com>
Signed-off-by: Taylor Blau <me@ttaylorr.com>
Signed-off-by: Derrick Stolee <derrickstolee@github.com>
---
 commit-graph.c | 64 +++++++++++++++++---------------------------------
 1 file changed, 21 insertions(+), 43 deletions(-)

diff --git a/commit-graph.c b/commit-graph.c
index 4356c8c1f4b..d1c98681e88 100644
--- a/commit-graph.c
+++ b/commit-graph.c
@@ -1559,13 +1559,31 @@ static void compute_topological_levels(struct write_commit_graph_context *ctx)
 	stop_progress(&ctx->progress);
 }
 
+static timestamp_t get_generation_from_graph_data(struct commit *c, void *data)
+{
+	return commit_graph_data_at(c)->generation;
+}
+
+static void set_generation_v2(struct commit *c, timestamp_t t, void *data)
+{
+	struct commit_graph_data *g = commit_graph_data_at(c);
+	g->generation = (uint32_t)t;
+}
+
 static void compute_generation_numbers(struct write_commit_graph_context *ctx)
 {
 	int i;
-	struct commit_list *list = NULL;
+	struct compute_generation_info info = {
+		.r = ctx->r,
+		.commits = &ctx->commits,
+		.get_generation = get_generation_from_graph_data,
+		.set_generation = set_generation_v2,
+		.data = ctx,
+	};
 
 	if (ctx->report_progress)
-		ctx->progress = start_delayed_progress(
+		info.progress = ctx->progress
+			      = start_delayed_progress(
 					_("Computing commit graph generation numbers"),
 					ctx->commits.nr);
 
@@ -1577,47 +1595,7 @@ static void compute_generation_numbers(struct write_commit_graph_context *ctx)
 		}
 	}
 
-	for (i = 0; i < ctx->commits.nr; i++) {
-		struct commit *c = ctx->commits.list[i];
-		timestamp_t corrected_commit_date;
-
-		repo_parse_commit(ctx->r, c);
-		corrected_commit_date = commit_graph_data_at(c)->generation;
-
-		display_progress(ctx->progress, i + 1);
-		if (corrected_commit_date != GENERATION_NUMBER_ZERO)
-			continue;
-
-		commit_list_insert(c, &list);
-		while (list) {
-			struct commit *current = list->item;
-			struct commit_list *parent;
-			int all_parents_computed = 1;
-			timestamp_t max_corrected_commit_date = 0;
-
-			for (parent = current->parents; parent; parent = parent->next) {
-				repo_parse_commit(ctx->r, parent->item);
-				corrected_commit_date = commit_graph_data_at(parent->item)->generation;
-
-				if (corrected_commit_date == GENERATION_NUMBER_ZERO) {
-					all_parents_computed = 0;
-					commit_list_insert(parent->item, &list);
-					break;
-				}
-
-				if (corrected_commit_date > max_corrected_commit_date)
-					max_corrected_commit_date = corrected_commit_date;
-			}
-
-			if (all_parents_computed) {
-				pop_commit(&list);
-
-				if (current->date && current->date > max_corrected_commit_date)
-					max_corrected_commit_date = current->date - 1;
-				commit_graph_data_at(current)->generation = max_corrected_commit_date + 1;
-			}
-		}
-	}
+	compute_reachable_generation_numbers(&info, 2);
 
 	for (i = 0; i < ctx->commits.nr; i++) {
 		struct commit *c = ctx->commits.list[i];
-- 
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