branch: git branch upstream merge has been exposed.

include/git2/branch.h

@@ -305,6 +305,19 @@ GIT_EXTERN(int) git_branch_remote_name(
  GIT_EXTERN(int) git_branch_upstream_remote(git_buf *buf, git_repository *repo, const char *refname);
 
 /**
+ * Retrieve the upstream merge of a local branch
+ *
+ * This will return the currently configured "branch.*.merge" for a given
+ * branch. This branch must be local.
+ *
+ * @param buf the buffer into which to write the name
+ * @param repo the repository in which to look
+ * @param refname the full name of the branch
+ * @return 0 or an error code
+ */
+ GIT_EXTERN(int) git_branch_upstream_merge(git_buf *buf, git_repository *repo, const char *refname);
+
+/**
  * Determine whether a branch name is valid, meaning that (when prefixed
  * with `refs/heads/`) that it is a valid reference name, and that any
  * additional branch name restrictions are imposed (eg, it cannot start

src/branch.c

@@ -492,6 +492,14 @@ static int git_branch_upstream_with_format(git_buf *buf, git_repository *repo, c
 	return error;
 }
 
+int git_branch_upstream_remote(git_buf *buf, git_repository *repo, const char *refname) {
+	git_branch_upstream_with_format(buf, repo, refname, "branch.%s.remote");
+}
+
+int git_branch_upstream_merge(git_buf *buf, git_repository *repo, const char *refname) {
+	git_branch_upstream_with_format(buf, repo, refname, "branch.%s.merge");
+}
+
 int git_branch_remote_name(git_buf *buf, git_repository *repo, const char *refname)
 {
 	git_strarray remote_list = {0};