Merge branch 'en/diffcore-rename'

Performance optimization work on the rename detection continues. * en/diffcore-rename: merge-ort: call diffcore_rename() directly gitdiffcore doc: mention new preliminary step for rename detection diffcore-rename: guide inexact rename detection based on basenames diffcore-rename: complete find_basename_matches() diffcore-rename: compute basenames of source and dest candidates t4001: add a test comparing basename similarity and content similarity diffcore-rename: filter rename_src list when possible diffcore-rename: no point trying to find a match better than exact