Merge branch 'jc/rename-degrade-cc-to-c' into maint

* jc/rename-degrade-cc-to-c: diffcore-rename: fall back to -C when -C -C busts the rename limit diffcore-rename: record filepair for rename src diffcore-rename: refactor "too many candidates" logic builtin/diff.c: remove duplicated call to diff_result_code()