[glib] gerror: Add (optional) annotation to g_propagate_error()

[Philip Withnall <pwithnall src gnome org>]

commit 0cc8c0f3e1230f8a3d6d7ed53523c2045d43ea63
Author: Philip Withnall <philip withnall collabora co uk>
Date:   Thu Oct 8 11:16:02 2015 +0100

    gerror: Add (optional) annotation to g_propagate_error()
    
    Also clarify in the documentation that @src must be non-%NULL.

 glib/gerror.c |    6 ++++--
 1 files changed, 4 insertions(+), 2 deletions(-)
---
diff --git a/glib/gerror.c b/glib/gerror.c
index 42eca90..9263ce9 100644
--- a/glib/gerror.c
+++ b/glib/gerror.c
@@ -626,12 +626,14 @@ g_set_error_literal (GError      **err,
 
 /**
  * g_propagate_error:
- * @dest: error return location
- * @src: error to move into the return location
+ * @dest: (out callee-allocates) (optional) (nullable): error return location
+ * @src: (transfer full): error to move into the return location
  *
  * If @dest is %NULL, free @src; otherwise, moves @src into * dest 
  * The error variable @dest points to must be %NULL.
  *
+ * @src must be non-%NULL.
+ *
  * Note that @src is no longer valid after this call. If you want
  * to keep using the same GError*, you need to set it to %NULL
  * after calling this function on it.