repo: create a tombstone commit when deleting a commit

When a commit is deleted and the repo is configured to use tombstone
commits, create one.  Delete the tombstone file only if the commit is
pulled again.

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

src/libostree/ostree-repo-commit.c

@@ -770,6 +770,28 @@ write_object (OstreeRepo         *self,
                                         cancellable, error))
         goto out;
 
+
+      if (objtype == OSTREE_OBJECT_TYPE_COMMIT)
+        {
+          GError *local_error = NULL;
+          /* If we are writing a commit, be sure there is no tombstone for it.
+             We may have deleted the commit and now we are trying to pull it again.  */
+          if (!ostree_repo_delete_object (self,
+                                          OSTREE_OBJECT_TYPE_TOMBSTONE_COMMIT,
+                                          actual_checksum,
+                                          cancellable,
+                                          &local_error))
+            {
+              if (g_error_matches (local_error, G_IO_ERROR, G_IO_ERROR_NOT_FOUND))
+                g_clear_error (&local_error);
+              else
+                {
+                  g_propagate_error (error, local_error);
+                  goto out;
+                }
+            }
+        }
+
       if (OSTREE_OBJECT_TYPE_IS_META (objtype))
         {
           if (G_UNLIKELY (file_object_length > OSTREE_MAX_METADATA_WARN_SIZE))