My Emacs configuration https://git.cjennings.net/dotemacs/atom?h=main 2026-05-10T18:41:27+00:00 2026-05-10T18:41:27+00:00 Craig Jennings c@cjennings.net 2026-05-10T18:41:27+00:00 urn:sha1:09f3349af22c932a01f0788787cee9ab4f3c38a7 `cj/dired-ediff-files' had its pair-determination logic inline: count check, prompt fallback when only one file was marked, and the older-first ordering for `ediff-files'. Lift it into `cj/--ediff-pair-from-files' -- pure given the file list, an injected prompt thunk, and a newer-than-p comparator -- so tests stay independent of mtimes and the dired prompt. While extracting, surface a latent bug: with zero marked files the original code fell through to `(file-newer-than-file-p nil nil)' and crashed with a wrong-type-argument error. Replace the crash with a clear `user-error' ("No files marked"), and add a regression test. The 3+ files case keeps its existing user-error message. Five Normal/Boundary/Error tests cover both ordering directions, the one-file prompt path, and both error counts.