[libgit2-glib] ggit-diff-hunk.c: Fix return annotations

[Igor Gnatenko <ignatenko src gnome org>]

commit 66fbef7baeb7abcbd9c1bfeb963a375472b28e6f
Author: Brian C. Lane <bcl redhat com>
Date:   Wed Aug 30 16:31:54 2017 -0700

    ggit-diff-hunk.c: Fix return annotations
    
    Add (nullable) as needed.

 libgit2-glib/ggit-diff-hunk.c |    2 +-
 1 files changed, 1 insertions(+), 1 deletions(-)
---
diff --git a/libgit2-glib/ggit-diff-hunk.c b/libgit2-glib/ggit-diff-hunk.c
index 78f1f25..cd0df99 100644
--- a/libgit2-glib/ggit-diff-hunk.c
+++ b/libgit2-glib/ggit-diff-hunk.c
@@ -64,7 +64,7 @@ _ggit_diff_hunk_wrap (const git_diff_hunk *hunk)
  * Atomically increments the reference count of @hunk by one.
  * This function is MT-safe and may be called from any thread.
  *
- * Returns: a #GgitDiffHunk.
+ * Returns: (transfer none) (nullable): a #GgitDiffHunk or %NULL.
  **/
 GgitDiffHunk *
 ggit_diff_hunk_ref (GgitDiffHunk *hunk)