revwalk: allow simplifying by first-parent

When enabled, only the first parent of each commit will be queued,
enabling a simple way of using first-parent simplification.

1 files changed, 18 insertions, 4 deletions

diff --git a/src/revwalk.c b/src/revwalk.c
index 1ff41bfb1..9e1e39ca4 100644
--- a/src/revwalk.c
+++ b/src/revwalk.c
@@ -99,10 +99,14 @@ static int process_commit(git_revwalk *walk, git_commit_list_node *commit, int h
 
 static int process_commit_parents(git_revwalk *walk, git_commit_list_node *commit)
 {
-	unsigned short i;
+	unsigned short i, max;
 	int error = 0;
 
-	for (i = 0; i < commit->out_degree && !error; ++i)
+	max = commit->out_degree;
+	if (walk->first_parent && commit->out_degree)
+		max = 1;
+
+	for (i = 0; i < max && !error; ++i)
 		error = process_commit(walk, commit->parents[i], commit->uninteresting);
 
 	return error;
@@ -333,7 +337,7 @@ static int revwalk_next_unsorted(git_commit_list_node **object_out, git_revwalk
 static int revwalk_next_toposort(git_commit_list_node **object_out, git_revwalk *walk)
 {
 	git_commit_list_node *next;
-	unsigned short i;
+	unsigned short i, max;
 
 	for (;;) {
 		next = git_commit_list_pop(&walk->iterator_topo);
@@ -347,7 +351,12 @@ static int revwalk_next_toposort(git_commit_list_node **object_out, git_revwalk
 			continue;
 		}
 
-		for (i = 0; i < next->out_degree; ++i) {
+
+		max = next->out_degree;
+		if (walk->first_parent && next->out_degree)
+			max = 1;
+
+		for (i = 0; i < max; ++i) {
 			git_commit_list_node *parent = next->parents[i];
 
 			if (--parent->in_degree == 0 && parent->topo_delay) {
@@ -505,6 +514,11 @@ void git_revwalk_sorting(git_revwalk *walk, unsigned int sort_mode)
 	}
 }
 
+void git_revwalk_simplify_first_parent(git_revwalk *walk)
+{
+	walk->first_parent = 1;
+}
+
 int git_revwalk_next(git_oid *oid, git_revwalk *walk)
 {
 	int error;