1 files changed, 57 insertions, 0 deletions
diff --git a/merge-base.c b/merge-base.c
new file mode 100644
index 0000000000..36ac42008c
--- /dev/null
+++ b/merge-base.c
@@ -0,0 +1,57 @@
+#include "cache.h"
+#include "revision.h"
+
+/*
+ * This is stupid. We could have much better heurstics, I bet.
+ */
+static int better(struct revision *new, struct revision *old)
+{
+	return new->date > old->date;
+}
+
+static struct revision *common_parent(struct revision *rev1, struct revision *rev2)
+{
+	int i;
+	struct revision *best = NULL;
+
+	mark_reachable(rev1, 1);
+	mark_reachable(rev2, 2);
+	for (i = 0; i < nr_revs ;i++) {
+		struct revision *rev = revs[i];
+		if ((rev->flags & 3) != 3)
+			continue;
+		if (!best) {
+			best = rev;
+			continue;
+		}
+		if (better(rev, best))
+			best = rev;
+	}
+	return best;
+}
+
+int main(int argc, char **argv)
+{
+	unsigned char rev1[20], rev2[20];
+	struct revision *common;
+
+	if (argc != 3 || get_sha1_hex(argv[1], rev1) || get_sha1_hex(argv[2], rev2))
+		usage("merge-base <commit1> <commit2>");
+
+	/*
+	 * We will eventually want to include a revision cache file
+	 * that "rev-tree.c" has generated, since this is going to
+	 * otherwise be quite expensive for big trees..
+	 *
+	 * That's some time off, though, and in the meantime we know
+	 * that we have a solution to the eventual expense.
+	 */
+	parse_commit(rev1);
+	parse_commit(rev2);
+
+	common = common_parent(lookup_rev(rev1), lookup_rev(rev2));
+	if (!common)
+		die("no common parent found");
+	printf("%s\n", sha1_to_hex(common->sha1));
+	return 0;
+}