** the "setting" command.  If no external diff program is configured, then
** the "-i" option is a no-op.  The "-i" option converts "gdiff" into "diff".
**
** The "-N" or "--new-file" option causes the complete text of added or
** deleted files to be displayed.
**
** Options:
**   --branch BRANCH     Show diff of all changes on BRANCH
**   --brief             Show filenames only
**   --context|-c N      Use N lines of context 
**   --from|-r VERSION   select VERSION as source for the diff
**   -i                  use internal diff logic
**   --new-file|-N       output complete text of added or deleted files
**   --to VERSION        select VERSION as target for the diff
**   --side-by-side|-y   side-by-side diff
**   --width|-W N        Width of lines in side-by-side diff 
*/
void diff_cmd(void){
  int isGDiff;               /* True for gdiff.  False for normal diff */
  int isInternDiff;          /* True for internal diff */
  int hasNFlag;              /* True if -N or --new-file flag is used */
  const char *zFrom;         /* Source version number */
  const char *zTo;           /* Target version number */
  const char *zBranch;       /* Branch to diff */
  const char *zDiffCmd = 0;  /* External diff command. NULL for internal diff */
  int diffFlags = 0;         /* Flags to control the DIFF */
  int f;

  isGDiff = g.argv[1][0]=='g';
  isInternDiff = find_option("internal","i",0)!=0;
  zFrom = find_option("from", "r", 1);
  zTo = find_option("to", 0, 1);
  zBranch = find_option("branch", 0, 1);
  diffFlags = diff_options();
  hasNFlag = find_option("new-file","N",0)!=0;
  if( hasNFlag ) diffFlags |= DIFF_NEWFILE;

  if( zBranch ){
    if( zTo || zFrom ){
      fossil_fatal("cannot use --from or --to with --branch");
    }
    zTo = zBranch;
    zFrom = mprintf("root:%s", zBranch);
  }
  if( zTo==0 ){
    db_must_be_within_tree();
    verify_all_options();
    if( !isInternDiff ){
      zDiffCmd = db_get(isGDiff ? "gdiff-command" : "diff-command", 0);
    }
    if( g.argc>=3 ){

** manifest.  Return the number of errors.
*/
static Manifest *vdiff_parse_manifest(const char *zParam, int *pRid){
  int rid;

  *pRid = rid = name_to_rid_www(zParam);
  if( rid==0 ){
    const char *z = P(zParam);
    if( z==0 || z[0]==0 ){
      webpage_error("Missing \"%s\" query parameter.", zParam);
    }else{
      webpage_error("No such artifact: \"%s\"", z);
    }
    return 0;
  }
  if( !is_a_version(rid) ){
    webpage_error("Artifact %s is not a checkin.", P(zParam));
    return 0;
  }
  return manifest_get(rid, CFTYPE_MANIFEST);

void vdiff_page(void){
  int ridFrom, ridTo;
  int showDetail = 0;
  int sideBySide = 0;
  int diffFlags = 0;
  Manifest *pFrom, *pTo;
  ManifestFile *pFileFrom, *pFileTo;
  const char *zBranch;

  login_check_credentials();
  if( !g.perm.Read ){ login_needed(); return; }
  login_anonymous_available();

  zBranch = P("branch");
  if( zBranch && zBranch[0] ){
    cgi_replace_parameter("from", mprintf("root:%s", zBranch));
    cgi_replace_parameter("to", zBranch);
  }
  pTo = vdiff_parse_manifest("to", &ridTo);
  if( pTo==0 ) return;
  pFrom = vdiff_parse_manifest("from", &ridFrom);
  if( pFrom==0 ) return;
  sideBySide = atoi(PD("sbs","1"));
  showDetail = atoi(PD("detail","0"));
  if( !showDetail && sideBySide ) showDetail = 1;
  if( !sideBySide ){
    style_submenu_element("Side-by-side Diff", "sbsdiff",
                          "%s/vdiff?from=%T&to=%T&detail=%d&sbs=1",
                          g.zTop, P("from"), P("to"), showDetail);

       " WHERE tag.tagname='sym-%q' "
       "   AND tagxref.tagid=tag.tagid AND tagxref.tagtype>0 "
       "   AND event.objid=tagxref.rid "
       "   AND event.type GLOB '%q'"
       " ORDER BY event.mtime DESC /*sort*/",
       &zTag[4], zType
    );
  }
  
  /* root:TAG -> The origin of the branch */
  if( memcmp(zTag, "root:", 5)==0 ){
    Stmt q;
    int rc;
    rid = symbolic_name_to_rid(zTag+5, zType);
    db_prepare(&q,
      "SELECT pid, EXISTS(SELECT 1 FROM tagxref"
                         " WHERE tagid=%d AND tagtype>0"
                         "   AND value=%Q AND rid=plink.pid)"
      "  FROM plink"
      " WHERE cid=:cid AND isprim",
      TAG_BRANCH, &zTag[5]
    );
    do{
      db_reset(&q);
      db_bind_int(&q, ":cid", rid);
      rc = db_step(&q);
      if( rc!=SQLITE_ROW ) break;
      rid = db_column_int(&q, 0);
    }while( db_column_int(&q, 1)==1 && rid>0 );
    db_finalize(&q);
    return rid;
  }

  /* symbolic-name ":" date-time */
  nTag = strlen(zTag);
  for(i=0; i<nTag-10 && zTag[i]!=':'; i++){}
  if( zTag[i]==':' && is_date(&zTag[i+1]) ){