[PATCH v6 2/3] revision: add peek functions for lookahead

[Pablo Sabater <pabloosabaterr@gmail.com>]

The graph code in a subsequent commit needs to be able to look ahead in
order to set indentation-related flags.

Using revs->commits is brittle and the data structure that holds the
pending commits might change in the future.

Add two functions that abstract this for the graph.

Helped-by: Kristofer Karlsson <stoansen@gmail.com>
Signed-off-by: Pablo Sabater <pabloosabaterr@gmail.com>
---
 revision.c | 38 ++++++++++++++++++++++++++++++++++++++
 revision.h | 10 ++++++++++
 2 files changed, 48 insertions(+)

diff --git a/revision.c b/revision.c
index e91d7e1f11..a472a28853 100644
--- a/revision.c
+++ b/revision.c
@@ -3708,6 +3708,44 @@ static unsigned int count_explore_walked;
 static unsigned int count_indegree_walked;
 static unsigned int count_topo_walked;
 
+struct commit *revision_peek_next_commit (struct rev_info *revs)
+{
+	struct topo_walk_info *info = revs->topo_walk_info;
+
+	if (info)
+		return prio_queue_peek(&info->topo_queue);
+	if (revs->commits)
+		return revs->commits->item;
+
+	return NULL;
+}
+
+int revision_has_commits_after (struct rev_info *revs, int n)
+{
+	struct topo_walk_info *info = revs->topo_walk_info;
+
+	if (info) {
+		int visible = 0;
+		for (size_t i = 0; i < info->topo_queue.nr && visible < n; i++) {
+			struct commit *c = info->topo_queue.array[i].data;
+			if (get_commit_action(revs, c) == commit_show)
+				visible++;
+		}
+		return visible > n-1;
+	}
+	if (revs->commits) {
+		struct commit_list *cl;
+		int visible = 0;
+		for (cl = revs->commits; cl && visible < n; cl = cl->next) {
+			if (get_commit_action(revs, cl->item) == commit_show)
+				visible++;
+		}
+		return visible > n-1;
+	}
+
+	return 0;
+}
+
 static void trace2_topo_walk_statistics_atexit(void)
 {
 	struct json_writer jw = JSON_WRITER_INIT;
diff --git a/revision.h b/revision.h
index 00c392be37..a10c6b0940 100644
--- a/revision.h
+++ b/revision.h
@@ -572,4 +572,14 @@ int rewrite_parents(struct rev_info *revs,
  */
 struct commit_list *get_saved_parents(struct rev_info *revs, const struct commit *commit);
 
+/*
+ * Peek into revision's next commit without consuming it.
+ */
+struct commit *revision_peek_next_commit(struct rev_info *revs);
+
+/*
+ * Check if there are n more commits to be shown yet.
+ */
+int revision_has_commits_after(struct rev_info *revs, int n);
+
 #endif

-- 
2.54.0