** NULL then the compile-time default is used (which gets propagated
** to JS-side state by certain pages).
*/
int diff_context_lines(DiffConfig *pCfg){
  const int dflt = 5;
  if(pCfg!=0){
    int n = pCfg->nContext;
    if( n==0 && (pCfg->diffFlags & DIFF_CONTEXT_EX)==0 ) n = dflt;
    return n<0 ? 0x7ffffff : n;
  }else{
    return dflt;
  }
}

/*
** Extract the width of columns for side-by-side diff.  Supply an

    }

    /* Undocumented and unsupported flags used for development
    ** debugging and analysis: */
    if( find_option("debug",0,0)!=0 ) diffFlags |= DIFF_DEBUG;
    if( find_option("raw",0,0)!=0 )   diffFlags |= DIFF_RAW;
  }
  if( (z = find_option("context","c",1))!=0 && (f = atoi(z))!=0 ){
    pCfg->nContext = f;
    diffFlags |= DIFF_CONTEXT_EX;
  }
  if( (z = find_option("width","W",1))!=0 && (f = atoi(z))>0 ){
    pCfg->wColumn = f;
  }
  if( find_option("linenum","n",0)!=0 ) diffFlags |= DIFF_LINENO;

*/
void diff_begin(DiffConfig *pCfg){
  if( (pCfg->diffFlags & DIFF_BROWSER)!=0 ){
    tempDiffFilename = fossil_temp_filename();
    tempDiffFilename = sqlite3_mprintf("%z.html", tempDiffFilename);
    diffOut = fossil_freopen(tempDiffFilename,"wb",stdout);
    if( diffOut==0 ){
      fossil_fatal("unable to create temporary file \"%s\"",
                   tempDiffFilename);
    }
#ifndef _WIN32
    signal(SIGINT, diff_www_interrupt);
#else
    SetConsoleCtrlHandler(diff_console_ctrl_handler, TRUE);
#endif

**                               as binary
**   --branch BRANCH             Show diff of all changes on BRANCH
**   --brief                     Show filenames only
**   -b|--browser                Show the diff output in a web-browser
**   --by                        Shorthand for "--browser -y"
**   -ci|--checkin VERSION       Show diff of all changes in VERSION
**   --command PROG              External diff program. Overrides "diff-command"
**   -c|--context N              Show N lines of context around each change, with
**                               negative N meaning show all content
**   --diff-binary BOOL          Include binary files with external commands
**   --exec-abs-paths            Force absolute path names on external commands
**   --exec-rel-paths            Force relative path names on external commands
**   -r|--from VERSION           Select VERSION as source for the diff
**   -w|--ignore-all-space       Ignore white space when comparing lines
**   -i|--internal               Use internal diff logic
**   --json                      Output formatted as JSON