Called after finding a file and by the default revert function.
Sets buffer mode, parses local variables.
Optional args ERROR, WARN, and NOAUTO: ERROR non-nil means there was an
error in reading the file. WARN non-nil means warn if there
exists an auto-save file more recent than the visited file.
NOAUTO means don't mess with auto-save mode.
Fourth arg AFTER-FIND-FILE-FROM-REVERT-BUFFER is ignored
(see `revert-buffer-in-progress-p' for similar functionality).
Fifth arg NOMODES non-nil means don't alter the file's modes.
Finishes by calling the functions in `find-file-hook' unless NOMODES is non-nil.