** check-out are used.
**
** The "-i" command-line option forces the use of the internal diff logic
** rather than any external diff program that might be configured using
** the <a>setting</a> command. If no external diff program is configured, then
** the "-i" option is a no-op.  The "-i" option converts "gdiff" into
** "diff".
**
** The results of the internal diff command can also be seen in the gui:
**  1. Go to the <a href="vdiff">vdiff</a> page
**  2. use the "diff against another version" link on the Check-in detail view.
*/
void diff_cmd(void){
  int isGDiff;               /* True for gdiff.  False for normal diff */
  int isInternDiff;          /* True for internal diff */
  const char *zFrom;         /* Source version number */
  const char *zTo;           /* Target version number */
  const char *zDiffCmd = 0;  /* External diff command. NULL for internal diff */