** Use the internal diff logic if zDiffCmd is NULL.  Otherwise call the
** command zDiffCmd to do the diffing.
*/
static void diff_file(
  Blob *pFile1,             /* In memory content to compare from */
  const char *zFile2,       /* On disk content to compare to */
  const char *zName,        /* Display name of the file */
  const char *zDiffCmd,     /* Command for comparison */
  int ignoreEolWs           /* Ignore whitespace at end of lines */
){
  if( zDiffCmd==0 ){
    Blob out;      /* Diff output text */
    Blob file2;    /* Content of zFile2 */

    /* Read content of zFile2 into memory */
    blob_zero(&file2);
    blob_read_from_file(&file2, zFile2);

    /* Compute and output the differences */
    blob_zero(&out);
    text_diff(pFile1, &file2, &out, 5, ignoreEolWs);
    printf("--- %s\n+++ %s\n", zName, zName);
    printf("%s\n", blob_str(&out));

    /* Release memory resources */
    blob_reset(&file2);
    blob_reset(&out);
  }else{

** Use the internal diff logic if zDiffCmd is NULL.  Otherwise call the
** command zDiffCmd to do the diffing.
*/
static void diff_file_mem(
  Blob *pFile1,             /* In memory content to compare from */
  Blob *pFile2,             /* In memory content to compare to */
  const char *zName,        /* Display name of the file */
  const char *zDiffCmd,     /* Command for comparison */
  int ignoreEolWs           /* Ignore whitespace at end of lines */
){
  if( zDiffCmd==0 ){
    Blob out;      /* Diff output text */

    blob_zero(&out);
    text_diff(pFile1, pFile2, &out, 5, ignoreEolWs);
    printf("--- %s\n+++ %s\n", zName, zName);
    printf("%s\n", blob_str(&out));

    /* Release memory resources */
    blob_reset(&out);
  }else{
    Blob cmd;

  }
}

/*
** Do a diff against a single file named in g.argv[2] from version zFrom
** against the same file on disk.
*/
static void diff_one_against_disk(
  const char *zFrom,        /* Name of file */
  const char *zDiffCmd,     /* Use this "diff" command */
  int ignoreEolWs           /* Ignore whitespace changes at end of lines */
){
  Blob fname;
  Blob content;
  file_tree_name(g.argv[2], &fname, 1);
  historical_version_of_file(zFrom, blob_str(&fname), &content, 0);
  diff_file(&content, g.argv[2], g.argv[2], zDiffCmd, ignoreEolWs);
  blob_reset(&content);
  blob_reset(&fname);
}

/*
** Run a diff between the version zFrom and files on disk.  zFrom might
** be NULL which means to simply show the difference between the edited
** files on disk and the check-out on which they are based.
*/
static void diff_all_against_disk(
  const char *zFrom,        /* Version to difference from */
  const char *zDiffCmd,     /* Use this diff command.  NULL for built-in */
  int ignoreEolWs           /* Ignore end-of-line whitespace */
){
  int vid;
  Blob sql;
  Stmt q;

  vid = db_lget_int("checkout", 0);
  vfile_check_signature(vid, 1);
  blob_zero(&sql);

      int srcid = db_column_int(&q, 4);
      Blob content;
      content_get(srcid, &content);
      printf("Index: %s\n======================================="
             "============================\n",
             zPathname
      );
      diff_file(&content, zFullName, zPathname, zDiffCmd, ignoreEolWs);
      blob_reset(&content);
    }
    free(zFullName);
  }
  db_finalize(&q);
  db_end_transaction(1);  /* ROLLBACK */
}

/*
** Output the differences between two versions of a single file.
** zFrom and zTo are the check-ins containing the two file versions.
** The filename is contained in g.argv[2].
*/
static void diff_one_two_versions(
  const char *zFrom,
  const char *zTo,
  const char *zDiffCmd,
  int ignoreEolWs
){
  char *zName;
  Blob fname;
  Blob v1, v2;
  file_tree_name(g.argv[2], &fname, 1);
  zName = blob_str(&fname);
  historical_version_of_file(zFrom, zName, &v1, 0);
  historical_version_of_file(zTo, zName, &v2, 0);
  diff_file_mem(&v1, &v2, zName, zDiffCmd, ignoreEolWs);
  blob_reset(&v1);
  blob_reset(&v2);
  blob_reset(&fname);
}

/*
** Output the differences between two check-ins.
*/
static void diff_all_two_versions(
  const char *zFrom,
  const char *zTo,
  const char *zDiffCmd,
  int ignoreEolWs
){
  Manifest mFrom, mTo;
  int iFrom, iTo;

  manifest_from_name(zFrom, &mFrom);
  manifest_from_name(zTo, &mTo);
  iFrom = iTo = 0;

      /* No changes */
      iFrom++;
      iTo++;
    }else{
      Blob f1, f2;
      int rid;
      printf("CHANGED %s\n", mFrom.aFile[iFrom].zName);
      printf("Index: %s\n======================================="
             "============================\n",
             mFrom.aFile[iFrom].zName
      );
      rid = uuid_to_rid(mFrom.aFile[iFrom].zUuid, 0);
      content_get(rid, &f1);
      rid = uuid_to_rid(mTo.aFile[iTo].zUuid, 0);
      content_get(rid, &f2);
      diff_file_mem(&f1, &f2, mFrom.aFile[iFrom].zName, zDiffCmd, ignoreEolWs);
      blob_reset(&f1);
      blob_reset(&f2);
      iFrom++;
      iTo++;
    }
  }
  manifest_clear(&mFrom);

  if( zTo==0 ){
    db_must_be_within_tree();
    verify_all_options();
    if( !isInternDiff && g.argc==3 ){
      zDiffCmd = db_get(isGDiff ? "gdiff-command" : "diff-command", 0);
    }
    if( g.argc==3 ){
      diff_one_against_disk(zFrom, zDiffCmd, 0);
    }else{
      diff_all_against_disk(zFrom, zDiffCmd, 0);
    }
  }else if( zFrom==0 ){
    fossil_fatal("must use --from if --to is present");
  }else{
    db_find_and_open_repository(1);
    verify_all_options();
    if( !isInternDiff ){
      zDiffCmd = db_get(isGDiff ? "gdiff-command" : "diff-command", 0);
    }
    if( g.argc==3 ){
      diff_one_two_versions(zFrom, zTo, zDiffCmd, 0);
    }else{
      diff_all_two_versions(zFrom, zTo, zDiffCmd, 0);
    }
  }
}