** for the diff operation.  If not specified, the source check-in is the
** base check-in for the current check-out. Similarly, the "--to VERSION"
** option specifies the check-in from which the second version of the file
** or files is taken.  If there is no "--to" option then the (possibly edited)
** files in the current check-out are used.  The "--checkin VERSION" option
** shows the changes made by check-in VERSION relative to its primary parent.
** The "--branch BRANCHNAME" shows all the changes on the branch BRANCHNAME.
**
** With the "--from VERSION" option, if VERSION is actually a directory name
** (not a tag or check-in hash) then the files under that directory are used
** as the baseline for the diff.
**
** The "-i" command-line option forces the use of Fossil's own internal
** diff logic rather than any external diff program that might be configured
** using 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".
**

**   --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
**   --dark                      Use dark mode for the Tcl/Tk-based GUI and HTML
**   --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           Use VERSION as the baseline for the diff, or
**                               if VERSION is a directory name, use files in
**                               that directory as the baseline.
**   -w|--ignore-all-space       Ignore white space when comparing lines
**   -i|--internal               Use internal diff logic
**   --invert                    Invert the diff
**   --json                      Output formatted as JSON
**   -n|--linenum                Show line numbers
**   -N|--new-file               Alias for --verbose
**   --numstat                   Show only the number of added and deleted lines
**   -y|--side-by-side           Side-by-side diff
**   --strip-trailing-cr         Strip trailing CR
**   --tcl                       Tcl-formatted output used internally by --tk
**   --tclsh PATH                Tcl/Tk shell used for --tk (default: "tclsh")
**   --tk                        Launch a Tcl/Tk GUI for display
**   --to VERSION                Select VERSION as target for the diff

**   --undo                      Use the undo buffer as the baseline
**   --unified                   Unified diff
**   -v|--verbose                Output complete text of added or deleted files
**   -h|--versions               Show compared versions in the diff header
**   --webpage                   Format output as a stand-alone HTML webpage
**   -W|--width N                Width of lines in side-by-side diff
**   -Z|--ignore-trailing-space  Ignore changes to end-of-line whitespace
*/
void diff_cmd(void){
  int isGDiff;               /* True for gdiff.  False for normal diff */
  const char *zFrom;         /* Source version number */
  const char *zTo;           /* Target version number */
  const char *zCheckin;      /* Check-in version number */
  const char *zBranch;       /* Branch to diff */

  int againstUndo = 0;       /* Diff against files in the undo buffer */
  FileDirList *pFileDir = 0; /* Restrict the diff to these files */
  DiffConfig DCfg;           /* Diff configuration object */
  int bFromIsDir = 0;        /* True if zFrom is a directory name */

  if( find_option("tk",0,0)!=0 || has_option("tclsh") ){
    diff_tk("diff", 2);
    return;
  }
  isGDiff = g.argv[1][0]=='g';
  zFrom = find_option("from", "r", 1);
  zTo = find_option("to", 0, 1);
  zCheckin = find_option("checkin", "ci", 1);
  zBranch = find_option("branch", 0, 1);

  againstUndo = find_option("undo",0,0)!=0;




  if( againstUndo && (zFrom!=0 || zTo!=0 || zCheckin!=0 || zBranch!=0) ){
    fossil_fatal("cannot use --undo together with --from, --to, --checkin,"
                 " or --branch");
  }
  if( zBranch ){
    if( zTo || zFrom || zCheckin ){
      fossil_fatal("cannot use --from, --to, or --checkin with --branch");
    }
    zTo = zBranch;
    zFrom = mprintf("root:%s", zBranch);
  }
  if( zCheckin!=0 && (zFrom!=0 || zTo!=0) ){
    fossil_fatal("cannot use --checkin together with --from or --to");
  }


  if( 0==zCheckin ){
    if( zTo==0 || againstUndo ){
      db_must_be_within_tree();
    }else if( zFrom==0 ){
      fossil_fatal("must use --from if --to is present");
    }else{
      db_find_and_open_repository(0, 0);
    }
  }else{
    db_find_and_open_repository(0, 0);
  }
  determine_exec_relative_option(1);
  if( zFrom!=file_tail(zFrom)
   && file_isdir(zFrom, ExtFILE)==1
   && !db_exists("SELECT 1 FROM tag WHERE tagname='sym-%q'", zFrom)
  ){
    bFromIsDir = 1;
    if( zTo ){
      fossil_fatal("cannot use --to together with \"--from PATH\"");
    }
  }
  diff_options(&DCfg, isGDiff, 0);
  verify_all_options();
  g.diffCnt[0] = g.diffCnt[1] = g.diffCnt[2] = 0;
  if( g.argc>=3 ){
    int i;
    Blob fname;
    pFileDir = fossil_malloc( sizeof(*pFileDir) * (g.argc-1) );
    memset(pFileDir, 0, sizeof(*pFileDir) * (g.argc-1));

      " WHERE plink.cid=%d AND plink.isprim AND plink.pid=blob.rid",
      ridTo);
    if( zFrom==0 ){
      fossil_fatal("check-in %s has no parent", zTo);
    }
  }
  diff_begin(&DCfg);
  if( bFromIsDir ){
    diff_externbase_to_checkout(zFrom, &DCfg, pFileDir);
  }else if( againstUndo ){
    if( db_lget_int("undo_available",0)==0 ){
      fossil_print("No undo or redo is available\n");
      return;
    }
    diff_undo_to_checkout(&DCfg, pFileDir);
  }else if( zTo==0 ){

**                       fullchain.pem) taken from FILE.
**   --chroot DIR        Use directory for chroot instead of repository path
**   --ckout-alias NAME  Treat URIs of the form /doc/NAME/... as if they were
**                       /doc/ckout/...
**   --create            Create a new REPOSITORY if it does not already exist
**   --errorlog FILE     Append HTTP error messages to FILE
**   --extroot DIR       Document root for the /ext extension mechanism

**   --files GLOBLIST    Comma-separated list of glob patterns for static files
**   --fossilcmd PATH    The pathname of the "fossil" executable on the remote
**                       system when REPOSITORY is remote.
**   --from PATH         Use PATH as the diff baseline for the /ckout page
**   --localauth         Enable automatic login for requests from localhost
**   --localhost         Listen on 127.0.0.1 only (always true for "ui")
**   --https             Indicates that the input is coming through a reverse
**                       proxy that has already translated HTTPS into HTTP.
**   --jsmode MODE       Determine how JavaScript is delivered with pages.
**                       Mode can be one of:
**                          inline       All JavaScript is inserted inline at

  int fCreate = 0;           /* The --create flag */
  int fNoBrowser = 0;        /* Do not auto-launch web-browser */
  const char *zInitPage = 0; /* Start on this page.  --page option */
  int findServerArg = 2;     /* argv index for find_server_repository() */
  char *zRemote = 0;         /* Remote host on which to run "fossil ui" */
  const char *zJsMode;       /* The --jsmode parameter */
  const char *zFossilCmd =0; /* Name of "fossil" binary on remote system */
  const char *zFrom;         /* Value for --from */


#if USE_SEE
  db_setup_for_saved_encryption_key();
#endif

#if defined(_WIN32)

  zTimeout = find_option("max-latency",0,1);
#endif
  g.useLocalauth = find_option("localauth", 0, 0)!=0;
  Th_InitTraceLog();
  zPort = find_option("port", "P", 1);
  isUiCmd = g.argv[1][0]=='u';
  if( isUiCmd ){
    zFrom = find_option("from", 0, 1);
    zInitPage = find_option("page", "p", 1);
    if( zInitPage && zInitPage[0]=='/' ) zInitPage++;
    zFossilCmd = find_option("fossilcmd", 0, 1);
    if( zFrom && zInitPage==0 ){
      zInitPage = mprintf("ckout?exbase=%T", zFrom);
    }
  }
  zNotFound = find_option("notfound", 0, 1);
  allowRepoList = find_option("repolist",0,0)!=0;
  if( find_option("nocompress",0,0)!=0 ) g.fNoHttpCompress = 1;
  zAltBase = find_option("baseurl", 0, 1);
  fCreate = find_option("create",0,0)!=0;