Merge branch 'jk/has-uncommitted-changes-fix'

"git pull --rebase" on a corrupt HEAD caused a segfault.  In
general we substitute an empty tree object when running the in-core
equivalent of the diff-index command, and the codepath has been
corrected to do so as well to fix this issue.

* jk/has-uncommitted-changes-fix:
  has_uncommitted_changes(): fall back to empty tree

1 files changed, 10 insertions, 0 deletions

diff --git a/wt-status.c b/wt-status.c
index 8827a256d3..fadbed0de9 100644
--- a/wt-status.c
+++ b/wt-status.c
@@ -2340,7 +2340,17 @@ int has_uncommitted_changes(int ignore_submodules)
 	if (ignore_submodules)
 		rev_info.diffopt.flags.ignore_submodules = 1;
 	rev_info.diffopt.flags.quick = 1;
+
 	add_head_to_pending(&rev_info);
+	if (!rev_info.pending.nr) {
+		/*
+		 * We have no head (or it's corrupt); use the empty tree,
+		 * which will complain if the index is non-empty.
+		 */
+		struct tree *tree = lookup_tree(the_hash_algo->empty_tree);
+		add_pending_object(&rev_info, &tree->object, "");
+	}
+
 	diff_setup_done(&rev_info.diffopt);
 	result = run_diff_index(&rev_info, 1);
 	return diff_result_code(&rev_info.diffopt, result);