lib/commit: don't query devino cache for modified files

We can't use the cache if the file we want to commit has been modified
by the client through the modifier. In fact, the issue in #1165 was
already solved by the previous commit, in which we stopped calling
devino_cache_lookup() prematurely, because the dup'ed file_info here
doesn't even have a device/inode attribute, so we would always get a
cache miss. Though this is the more correct thing to do in general.

Closes: #1165

src/libostree/ostree-repo-commit.c

@@ -2557,6 +2557,7 @@ write_directory_content_to_mtree_internal (OstreeRepo                  *self,
   g_autoptr(GFileInfo) modified_info = NULL;
   OstreeRepoCommitFilterResult filter_result =
     _ostree_repo_commit_modifier_apply (self, modifier, child_relpath, child_info, &modified_info);
+  const gboolean child_info_was_modified = (child_info == modified_info);
 
   if (filter_result != OSTREE_REPO_COMMIT_FILTER_ALLOW)
     {
@@ -2618,16 +2619,20 @@ write_directory_content_to_mtree_internal (OstreeRepo                  *self,
   else
     {
       guint64 file_obj_length;
-      const char *loose_checksum;
       g_autoptr(GInputStream) file_input = NULL;
       g_autoptr(GVariant) xattrs = NULL;
       g_autoptr(GInputStream) file_object_input = NULL;
       g_autofree guchar *child_file_csum = NULL;
       g_autofree char *tmp_checksum = NULL;
 
-      loose_checksum = devino_cache_lookup (self, modifier,
-                                            g_file_info_get_attribute_uint32 (child_info, "unix::device"),
-                                            g_file_info_get_attribute_uint64 (child_info, "unix::inode"));
+      /* only check the devino cache if the file info was not modified */
+      const char *loose_checksum = NULL;
+      if (!child_info_was_modified)
+        {
+          guint32 dev = g_file_info_get_attribute_uint32 (child_info, "unix::device");
+          guint64 inode = g_file_info_get_attribute_uint64 (child_info, "unix::inode");
+          loose_checksum = devino_cache_lookup (self, modifier, dev, inode);
+        }
 
       if (loose_checksum)
         {