[libgit2-glib] Fix const warnings

[Paolo Borelli <pborelli src gnome org>]

commit d6bf26731ceb5955207db80b874b846757b404fd
Author: Paolo Borelli <pborelli gnome org>
Date:   Sat Oct 12 15:36:25 2013 +0200

    Fix const warnings

 libgit2-glib/ggit-diff-patch.c |   14 +++++---------
 1 files changed, 5 insertions(+), 9 deletions(-)
---
diff --git a/libgit2-glib/ggit-diff-patch.c b/libgit2-glib/ggit-diff-patch.c
index a96bff8..41fa249 100644
--- a/libgit2-glib/ggit-diff-patch.c
+++ b/libgit2-glib/ggit-diff-patch.c
@@ -93,24 +93,20 @@ gchar *
 ggit_diff_patch_to_string (GgitDiffPatch  *diff_patch,
                            GError        **error)
 {
-       const gchar *retval;
-       const gchar *result;
+       char *retval;
+       gchar *result = NULL;
        gint ret;
 
        g_return_val_if_fail (diff_patch != NULL, NULL);
        g_return_val_if_fail (error == NULL || *error == NULL, NULL);
 
-
        ret = git_diff_patch_to_str (&retval, diff_patch->diff_patch);
-
-       if (ret != GIT_OK)
+       if (ret == GIT_OK)
        {
-               return NULL;
+               result = g_strdup (retval);
+               g_free (retval);
        }
 
-       result = g_strdup (retval);
-       g_free (retval);
-
        return result;
 }