Talk about <read-cache.c> and <cache-tree.c>, things like:
cache → the_index macros
read_index()
write_index()
ie_match_stat() and ie_modified(); how they are different and when to use which.
index_name_pos()
remove_index_entry_at()
remove_file_from_index()
add_file_to_index()
add_index_entry()
refresh_index()
discard_index()
cache_tree_invalidate_path()
cache_tree_update()
(JC, Linus)