In follow mode, reopen file if it shrinks.

ch.c

@@ -316,13 +316,16 @@ ch_get()
 #if HAVE_STAT_INO
  if (follow_mode == FOLLOW_NAME)
  {
- /* See whether the file's i-number has changed.
+ /* See whether the file's i-number has changed,
+ * or the file has shrunk.
  * If so, force the file to be closed and
  * reopened. */
  struct stat st;
+ POSITION curr_pos = ch_tell();
  int r = stat(get_filename(curr_ifile), &st);
  if (r == 0 && (st.st_ino != curr_ino ||
- st.st_dev != curr_dev))
+ st.st_dev != curr_dev ||
+ (curr_pos != NULL_POSITION && st.st_size < curr_pos)))
  {
  /* screen_trashed=2 causes
  * make_display to reopen the file. */