merge-ort: add outline of get_provisional_directory_renames()
This function is based on merge-recursive.c's get_directory_renames(),
except that the first half has been split out into a not-yet-implemented
compute_rename_counts(). The primary difference here is our lack of the
non_unique_new_dir boolean in our strmap. The lack of that field will
at first cause us to fail testcase 2b of t6423; however, future
optimizations will obviate the need for that ugly field so we have just
left it out.
Signed-off-by: Elijah Newren <newren@gmail.com>
Signed-off-by: Junio C Hamano <gitster@pobox.com>