[PATCH 09/10] Introduce get_octopus_merge_bases() in commit.c

[Miklos Vajna <vmiklos@frugalware.org>]

This is like get_merge_bases() but it works for multiple heads, like
show-branch --merge-base.

Signed-off-by: Miklos Vajna <vmiklos@frugalware.org>
---
 commit.c |   32 ++++++++++++++++++++++++++++++++
 commit.h |    1 +
 2 files changed, 33 insertions(+), 0 deletions(-)

diff --git a/commit.c b/commit.c
index 6ba5acb..c09b305 100644
--- a/commit.c
+++ b/commit.c
@@ -625,6 +625,38 @@ static struct commit_list *merge_bases(struct commit *one, struct commit *two)
 	return result;
 }
 
+struct commit_list *get_octopus_merge_bases(struct commit_list *in, int cleanup)
+{
+	struct commit_list *i, *j, *k, *ret = NULL;
+
+	for (i = in; i; i = i->next) {
+		if (!ret)
+			commit_list_append(i->item, &ret);
+		else {
+			struct commit_list *new = NULL, *end = NULL;
+
+			for (j = ret; j; j = j->next) {
+				struct commit_list *bases;
+				bases = get_merge_bases(i->item, j->item, cleanup);
+				/*
+				 * Now we just append bases to new, but
+				 * calling commit_list_append() for each
+				 * item would be expensive, so do it by
+				 * hand.
+				 */
+				if (!new)
+					new = bases;
+				else
+					end->next = bases;
+				for (k = bases; k; k = k->next)
+					end = k;
+			}
+			ret = new;
+		}
+	}
+	return ret;
+}
+
 struct commit_list *get_merge_bases(struct commit *one,
 					struct commit *two, int cleanup)
 {
diff --git a/commit.h b/commit.h
index 5d9ac43..201782d 100644
--- a/commit.h
+++ b/commit.h
@@ -122,6 +122,7 @@ int read_graft_file(const char *graft_file);
 struct commit_graft *lookup_commit_graft(const unsigned char *sha1);
 
 extern struct commit_list *get_merge_bases(struct commit *rev1, struct commit *rev2, int cleanup);
+extern struct commit_list *get_octopus_merge_bases(struct commit_list *in, int cleanup);
 
 extern int register_shallow(const unsigned char *sha1);
 extern int unregister_shallow(const unsigned char *sha1);
-- 
1.5.6.rc0.dirty