[ostree] sysroot-upgrader: Check merge deployment, not ref for differences

[Colin Walters <walters src gnome org>]

commit 913337c557d0be9a3b7b7f5251a5d12a33a5a937
Author: Colin Walters <walters verbum org>
Date:   Mon Mar 31 14:41:13 2014 -0400

    sysroot-upgrader: Check merge deployment, not ref for differences
    
    Otherwise this broke atomicity; we could fetch/store the ref, then
    crash, and then not upgrade the next time we tried upgrading.
    
    The correct model is: the tree has changed if the new ref is different
    from the merge deployment.

 src/libostree/ostree-sysroot-upgrader.c |    7 +++----
 1 files changed, 3 insertions(+), 4 deletions(-)
---
diff --git a/src/libostree/ostree-sysroot-upgrader.c b/src/libostree/ostree-sysroot-upgrader.c
index b95c448..c262f2b 100644
--- a/src/libostree/ostree-sysroot-upgrader.c
+++ b/src/libostree/ostree-sysroot-upgrader.c
@@ -431,7 +431,7 @@ ostree_sysroot_upgrader_pull (OstreeSysrootUpgrader  *self,
   gboolean ret = FALSE;
   gs_unref_object OstreeRepo *repo = NULL;
   char *refs_to_fetch[] = { self->origin_ref, NULL };
-  gs_free char *from_revision = NULL;
+  const char *from_revision = NULL;
   gs_free char *new_revision = NULL;
   gs_free char *origin_refspec = NULL;
 
@@ -443,9 +443,8 @@ ostree_sysroot_upgrader_pull (OstreeSysrootUpgrader  *self,
   else
     origin_refspec = g_strdup (self->origin_ref);
 
-  if (!ostree_repo_resolve_rev (repo, origin_refspec, TRUE, &from_revision,
-                                error))
-    goto out;
+  g_assert (self->merge_deployment);
+  from_revision = ostree_deployment_get_csum (self->merge_deployment);
 
   if (self->origin_remote)
     {