_ostree_repo_file_replace_contents: make buf const

Signed-off-by: Giuseppe Scrivano <gscrivan@redhat.com>

src/libostree/ostree-repo-private.h

@@ -130,7 +130,7 @@ gboolean
 _ostree_repo_file_replace_contents (OstreeRepo    *self,
                                     int            dfd,
                                     const char    *path,
-                                    guint8        *buf,
+                                    const guint8  *buf,
                                     gsize          len,
                                     GCancellable  *cancellable,
                                     GError       **error);

src/libostree/ostree-repo.c

@@ -1509,7 +1509,7 @@ gboolean
 _ostree_repo_file_replace_contents (OstreeRepo    *self,
                                     int            dfd,
                                     const char    *path,
-                                    guint8        *buf,
+                                    const guint8   *buf,
                                     gsize          len,
                                     GCancellable  *cancellable,
                                     GError       **error)