bug#15535: Acknowledgement (24.3.50; basic-save-buffer should update buffer-file-coding-system value if the contents were written using different coding system)

[Dmitry Gutov]

Sorry, here's a better test:

(ert-deftest save-buffer-updates-buffer-file-coding-system ()
  (let ((file (expand-file-name "foo" temporary-file-directory))
        (default-buffer-file-coding-system 'utf-8-unix))
    (find-file file)
    (insert "abcdef\n")
    (save-buffer)
    (kill-buffer)
    (unwind-protect
        (with-current-buffer (find-file-noselect file)
          (should (eq 'undecided (coding-system-change-eol-conversion
                                  buffer-file-coding-system nil)))
          (insert "водка матрёшка селёдка")
          (save-buffer)
          (let ((coding-system buffer-file-coding-system))
            (kill-buffer)
            (should (eq 'utf-8-unix coding-system))))
      (delete-file file))))

Likewise, succeeds on 24.3, fails on trunk.