t / t4135 / git-with backslash.diffon commit dir: convert read_skip_worktree_file_from_index to take an index (6f52b74)
   1diff --git "a/post\\image.txt" "b/post\\image.txt"
   2new file mode 100644
   3index 0000000..eff0c54
   4--- /dev/null
   5+++ "b/post\\image.txt"
   6@@ -0,0 +1 @@
   7+postimage