notes: add git_note_default_ref()

Add git_note_default_ref to allow easy retrieval of the currently set
default notes reference.

include/git2/notes.h

@@ -92,6 +92,16 @@ GIT_EXTERN(int) git_note_remove(git_repository *repo, const char *notes_ref,
  */
 GIT_EXTERN(void) git_note_free(git_note *note);
 
+/**
+ * Get the default notes reference for a repository
+ *
+ * @param out Pointer to the default notes reference
+ * @param repo The Git repository
+ *
+ * @return GIT_SUCCESS or an error code
+ */
+GIT_EXTERN(int) git_note_default_ref(const char **out, git_repository *repo);
+
 /** @} */
 GIT_END_DECL
 #endif

src/notes.c

@@ -417,6 +417,12 @@ int git_note_remove(git_repository *repo, const char *notes_ref,
 	return error;
 }
 
+int git_note_default_ref(const char **out, git_repository *repo)
+{
+	assert(repo);
+	return note_get_default_ref(out, repo);
+}
+
 const char * git_note_message(git_note *note)
 {
 	assert(note);

tests-clar/notes/notesref.c

 #include "clar_libgit2.h"
 
+#include "notes.h"
+
 static git_repository *_repo;
 static git_note *_note;
 static git_signature *_sig;
@@ -24,6 +26,7 @@ void test_notes_notesref__cleanup(void)
 void test_notes_notesref__config_corenotesref(void)
 {
 	git_oid oid, note_oid;
+	const char *default_ref;
 
 	cl_git_pass(git_signature_now(&_sig, "alice", "alice@example.com"));
 	cl_git_pass(git_oid_fromstr(&oid, "8496071c1b46c854b31185ea97743be6a8774479"));
@@ -43,4 +46,12 @@ void test_notes_notesref__config_corenotesref(void)
 	cl_git_pass(git_note_read(&_note, _repo, "refs/notes/mydefaultnotesref", &oid));
 	cl_assert(!strcmp(git_note_message(_note), "test123test\n"));
 	cl_assert(!git_oid_cmp(git_note_oid(_note), &note_oid));
+
+	cl_git_pass(git_note_default_ref(&default_ref, _repo));
+	cl_assert(!strcmp(default_ref, "refs/notes/mydefaultnotesref"));
+
+	cl_git_pass(git_config_delete(_cfg, "core.notesRef"));
+
+	cl_git_pass(git_note_default_ref(&default_ref, _repo));
+	cl_assert(!strcmp(default_ref, GIT_NOTES_DEFAULT_REF));
 }