Fossil

** set of flags suitable for passing to text_diff().
*/
void ajax_render_diff(Blob * pOrig, Blob *pContent, u64 diffFlags){
  Blob out = empty_blob;
  DiffConfig DCfg;

  diff_config_init(&DCfg, diffFlags);
  text_diff(pOrig, pContent, &out, &DCfg);
  if(blob_size(&out)==0){
    /* nothing to do */
  }else if(DIFF_SIDEBYSIDE & diffFlags){
    CX("%b",&out);
  }else{
    CX("<pre class='udiff'>%b</pre>",&out);
  }

**        TCL, JSON, HTML vs. plain-text).
**
**    *   Number of lines of context surrounding each difference block
**
**    *   Width of output columns for text side-by-side diffop          
*/
struct DiffConfig {
  u64 diffFlags;           /* Diff flags */
  u32 nFile;               /* Number of files diffed so far */
  const char *zDiffCmd;    /* External diff command to use instead of builtin */
  const char *zBinGlob;    /* GLOB pattern for binary files */
  ReCompiled *pRe;         /* Show only changes matching this pattern */
};

#endif /* INTERFACE */

/*
** Initialize memory for a DiffConfig based on just a diffFlags integer.
*/

}

/*
** Format a diff using a DiffBuilder object
*/
static void formatDiff(
  DContext *p,           /* The computed diff */

  DiffConfig *pCfg,      /* Configuration options */
  DiffBuilder *pBuilder  /* The formatter object */
){
  const DLine *A;        /* Left side of the diff */
  const DLine *B;        /* Right side of the diff */
  unsigned int a = 0;    /* Index of next line in A[] */
  unsigned int b = 0;    /* Index of next line in B[] */

    for(nr=1; R[r+nr*3]>0 && R[r+nr*3]<nContext*2; nr++){}

    /* If there is a regex, skip this block (generate no diff output)
    ** if the regex matches or does not match both insert and delete.
    ** Only display the block if one side matches but the other side does
    ** not.
    */
    if( pCfg->pRe ){
      int hideBlock = 1;
      int xa = a, xb = b;
      for(i=0; hideBlock && i<nr; i++){
        int c1, c2;
        xa += R[r+i*3];
        xb += R[r+i*3];
        c1 = re_dline_match(pCfg->pRe, &A[xa], R[r+i*3+1]);
        c2 = re_dline_match(pCfg->pRe, &B[xb], R[r+i*3+2]);
        hideBlock = c1==c2;
        xa += R[r+i*3+1];
        xb += R[r+i*3+2];
      }
      if( hideBlock ){
        a = xa;
        b = xb;

** file is encountered, 0 is returned and pOut is written with
** text "cannot compute difference between binary files".
*/
int *text_diff(
  Blob *pA_Blob,   /* FROM file */
  Blob *pB_Blob,   /* TO file */
  Blob *pOut,      /* Write diff here if not NULL */

  DiffConfig *pCfg /* Configuration options */
){
  int ignoreWs; /* Ignore whitespace */
  DContext c;

  pCfg->nFile++;
  if( pCfg->diffFlags & DIFF_INVERT ){
    Blob *pTemp = pA_Blob;
    pA_Blob = pB_Blob;
    pB_Blob = pTemp;
  }
  ignoreWs = (pCfg->diffFlags & DIFF_IGNORE_ALLWS)!=0;
  blob_to_utf8_no_bom(pA_Blob, 0);

      unsigned int r;
      for(r=0; R[r] || R[r+1] || R[r+2]; r += 3){
        blob_appendf(pOut, " copy %6d  delete %6d  insert %6d\n",
                     R[r], R[r+1], R[r+2]);
      }
    }else if( pCfg->diffFlags & DIFF_JSON ){
      DiffBuilder *pBuilder = dfjsonNew(pOut);
      formatDiff(&c, pCfg, pBuilder);
      blob_append_char(pOut, '\n');
    }else if( pCfg->diffFlags & DIFF_TCL ){
      DiffBuilder *pBuilder = dftclNew(pOut);
      formatDiff(&c, pCfg, pBuilder);
    }else if( pCfg->diffFlags & DIFF_SIDEBYSIDE ){
      DiffBuilder *pBuilder;
      if( pCfg->diffFlags & DIFF_HTML ){
        pBuilder = dfsplitNew(pOut);
      }else{
        pBuilder = dfsbsNew(pOut, pCfg);
      }
      formatDiff(&c, pCfg, pBuilder);
    }else if( pCfg->diffFlags & DIFF_DEBUG ){
      DiffBuilder *pBuilder = dfdebugNew(pOut);
      formatDiff(&c, pCfg, pBuilder);
    }else if( pCfg->diffFlags & DIFF_HTML ){
      DiffBuilder *pBuilder = dfunifiedNew(pOut);
      formatDiff(&c, pCfg, pBuilder);
    }else{
      contextDiff(&c, pOut, pCfg);
    }
    fossil_free(c.aFrom);
    fossil_free(c.aTo);
    fossil_free(c.aEdit);
    return 0;

**
** This command used to be called "test-diff".  The older "test-diff" spelling
** still works, for compatibility.
*/
void xdiff_cmd(void){
  Blob a, b, out;
  const char *zRe;           /* Regex filter for diff output */

  DiffConfig DCfg;

  if( find_option("tk",0,0)!=0 ){
    diff_tk("xdiff", 2);
    return;
  }
  find_option("i",0,0);
  find_option("v",0,0);
  diff_options(&DCfg, 0);
  zRe = find_option("regexp","e",1);
  if( zRe ){
    const char *zErr = re_compile(&DCfg.pRe, zRe, 0);
    if( zErr ) fossil_fatal("regex error: %s", zErr);
  }

  verify_all_options();
  if( g.argc!=4 ) usage("FILE1 FILE2");
  blob_zero(&out);
  diff_begin(&DCfg);
  diff_print_filenames(g.argv[2], g.argv[3], &DCfg, &out);
  blob_read_from_file(&a, g.argv[2], ExtFILE);
  blob_read_from_file(&b, g.argv[3], ExtFILE);
  text_diff(&a, &b, &out, &DCfg);
  blob_write_to_file(&out, "-");
  diff_end(&DCfg, 0);
  re_free(DCfg.pRe);
}

/**************************************************************************
** The basic difference engine is above.  What follows is the annotation
** engine.  Both are in the same file since they share many components.
*/

    if( pCfg->diffFlags & DIFF_BRIEF ){
      if( blob_compare(pFile1, &file2) ){
        fossil_print("CHANGED  %s\n", zName);
      }
    }else{
      blob_zero(&out);
      if( fSwapDiff ){
        text_diff(&file2, pFile1, &out, pCfg);
      }else{
        text_diff(pFile1, &file2, &out, pCfg);
      }
      if( blob_size(&out) ){
        if( pCfg->diffFlags & DIFF_NUMSTAT ){
          if( !diffBlob ){
            fossil_print("%s %s\n", blob_str(&out), zName);
          }else{
            blob_appendf(diffBlob, "%s %s\n", blob_str(&out), zName);

  DiffConfig *pCfg          /* Diff flags */
){
  if( pCfg->diffFlags & DIFF_BRIEF ) return;
  if( zDiffCmd==0 ){
    Blob out;      /* Diff output text */

    blob_zero(&out);
    text_diff(pFile1, pFile2, &out, pCfg);
    if( pCfg->diffFlags & DIFF_NUMSTAT ){
      fossil_print("%s %s\n", blob_str(&out), zName);
    }else{
      diff_print_filenames(zName, zName, pCfg, 0);
      fossil_print("%s\n", blob_str(&out));
    }

/*
** Append the difference between artifacts to the output
*/
static void append_diff(
  const char *zFrom,    /* Diff from this artifact */
  const char *zTo,      /*  ... to this artifact */
  DiffConfig *pCfg      /* The diff configuration */

){
  int fromid;
  int toid;
  Blob from, to;

  if( zFrom ){
    fromid = uuid_to_rid(zFrom, 0);
    content_get(fromid, &from);
  }else{
    blob_zero(&from);
  }
  if( zTo ){
    toid = uuid_to_rid(zTo, 0);
    content_get(toid, &to);
  }else{
    blob_zero(&to);
  }
  if( pCfg->diffFlags & DIFF_SIDEBYSIDE ){
    pCfg->diffFlags |= DIFF_HTML | DIFF_NOTTOOBIG;
  }else{
    pCfg->diffFlags |= DIFF_LINENO | DIFF_HTML | DIFF_NOTTOOBIG;
  }

  text_diff(&from, &to, cgi_output_blob(), pCfg);
  blob_reset(&from);
  blob_reset(&to);
}

/*
** Write a line of web-page output that shows changes that have occurred
** to a file between two check-ins.
*/
static void append_file_change_line(
  const char *zCkin,    /* The checkin on which the change occurs */
  const char *zName,    /* Name of the file that has changed */
  const char *zOld,     /* blob.uuid before change.  NULL for added files */
  const char *zNew,     /* blob.uuid after change.  NULL for deletes */
  const char *zOldName, /* Prior name.  NULL if no name change. */
  DiffConfig *pCfg,     /* Flags for text_diff() or NULL to omit all */

  int mperm             /* executable or symlink permission for zNew */
){
  @ <p>
  if( !g.perm.Hyperlink ){
    if( zNew==0 ){
      @ Deleted %h(zName).
    }else if( zOld==0 ){

        @ %h(zName) became a symlink.
      }else{
        @ %h(zName) became a regular file.
      }
    }else{
      @ Changes to %h(zName).
    }
    if( pCfg ){
      append_diff(zOld, zNew, pCfg);
    }
  }else{
    if( zOld && zNew ){
      if( fossil_strcmp(zOld, zNew)!=0 ){
        @ Modified %z(href("%R/finfo?name=%T&m=%!S&ci=%!S",zName,zNew,zCkin))\
        @ %h(zName)</a>
        @ from %z(href("%R/artifact/%!S",zOld))[%S(zOld)]</a>

    }else if( zOld ){
      @ Deleted %z(href("%R/finfo?name=%T&m=%!S&ci=%!S",zName,zOld,zCkin))\
      @ %h(zName)</a> version %z(href("%R/artifact/%!S",zOld))[%S(zOld)]</a>.
    }else{
      @ Added %z(href("%R/finfo?name=%T&m=%!S&ci=%!S",zName,zNew,zCkin))\
      @ %h(zName)</a> version %z(href("%R/artifact/%!S",zNew))[%S(zNew)]</a>.
    }
    if( pCfg ){
      append_diff(zOld, zNew, pCfg);
    }else if( zOld && zNew && fossil_strcmp(zOld,zNew)!=0 ){
      @ &nbsp;&nbsp;
      @ %z(href("%R/fdiff?v1=%!S&v2=%!S",zOld,zNew))[diff]</a>
    }
  }
  @ </p>
}

/*
** Generate javascript to enhance HTML diffs.
*/
void append_diff_javascript(int sideBySide){
  if( !sideBySide ) return;
  builtin_request_js("diff.js");
}

/*
** Construct an appropriate diffFlag for text_diff() based on query
** parameters and the to boolean arguments.
*/
DiffConfig *construct_diff_flags(int diffType, DiffConfig *pCfg){
  u64 diffFlags = 0;  /* Zero means do not show any diff */
  if( diffType>0 ){
    int x;
    if( diffType==2 ){
      diffFlags = DIFF_SIDEBYSIDE;

      /* "dw" query parameter determines width of each column */

    x = atoi(PD("dc","7"));
    if( x<0 || x>DIFF_CONTEXT_MASK ) x = DIFF_CONTEXT_MASK;
    diffFlags += x;

    /* The "noopt" parameter disables diff optimization */
    if( PD("noopt",0)!=0 ) diffFlags |= DIFF_NOOPT;
    diffFlags |= DIFF_STRIP_EOLCR;
    diff_config_init(pCfg, diffFlags);
    return pCfg;
  }else{
    diff_config_init(pCfg, 0);
    return 0;
  }
}

/*
** WEBPAGE: ci_tags
** URL:    /ci_tags?name=ARTIFACTID
**
** Show all tags and properties for a given check-in.

** or a tag or branch name that identifies the check-in.
*/
void ci_page(void){
  Stmt q1, q2, q3;
  int rid;
  int isLeaf;
  int diffType;        /* 0: no diff,  1: unified,  2: side-by-side */

  const char *zName;   /* Name of the check-in to be displayed */
  const char *zUuid;   /* Hash of zName, found via blob.uuid */
  const char *zParent; /* Hash of the parent check-in (if any) */
  const char *zRe;     /* regex parameter */
  ReCompiled *pRe = 0; /* regex */
  const char *zW;               /* URL param for ignoring whitespace */
  const char *zPage = "vinfo";  /* Page that shows diffs */
  const char *zPageHide = "ci"; /* Page that hides diffs */
  const char *zBrName;          /* Branch name */
  DiffConfig DCfg,*pCfg;        /* Type of diff */

  login_check_credentials();
  if( !g.perm.Read ){ login_needed(g.anon.Read); return; }
  style_set_current_feature("vinfo");
  zName = P("name");
  rid = name_to_rid_www("name");
  if( rid==0 ){

    wiki_render_associated("checkin", zUuid, 0);
  }
  render_backlink_graph(zUuid, "<div class=\"section\">References</div>\n");
  @ <div class="section">Context</div>
  render_checkin_context(rid, 0, 0, 0);
  @ <div class="section">Changes</div>
  @ <div class="sectionmenu">
  pCfg = construct_diff_flags(diffType, &DCfg);
  DCfg.pRe = pRe;  
  zW = (DCfg.diffFlags&DIFF_IGNORE_ALLWS)?"&w":"";
  if( diffType!=0 ){
    @ %z(chref("button","%R/%s/%T?diff=0",zPageHide,zName))\
    @ Hide&nbsp;Diffs</a>
  }
  if( diffType!=1 ){
    @ %z(chref("button","%R/%s/%T?diff=1%s",zPage,zName,zW))\
    @ Unified&nbsp;Diffs</a>

  while( db_step(&q3)==SQLITE_ROW ){
    const char *zName = db_column_text(&q3,0);
    int mperm = db_column_int(&q3, 1);
    const char *zOld = db_column_text(&q3,2);
    const char *zNew = db_column_text(&q3,3);
    const char *zOldName = db_column_text(&q3, 4);
    append_file_change_line(zUuid, zName, zOld, zNew, zOldName, 
                            pCfg,mperm);
  }
  db_finalize(&q3);
  append_diff_javascript(diffType);
  builtin_fossil_js_bundle_or("info-diff",NULL);
  style_finish_page();
}

/*
** WEBPAGE: winfo
** URL:  /winfo?name=HASH

**   inv             "Invert".  Exchange the roles of from= and to=
**
** Show all differences between two check-ins.
*/
void vdiff_page(void){
  int ridFrom, ridTo;
  int diffType = 0;        /* 0: none, 1: unified, 2: side-by-side */

  Manifest *pFrom, *pTo;
  ManifestFile *pFileFrom, *pFileTo;
  const char *zBranch;
  const char *zFrom;
  const char *zTo;
  const char *zRe;
  const char *zGlob;
  char *zMergeOrigin = 0;
  ReCompiled *pRe = 0;
  DiffConfig DCfg, *pCfg = 0;
  int graphFlags = 0;
  Blob qp;
  int bInvert = PB("inv");

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

      blob_appendf(&qp, "&glob=%T", zGlob);
    }
  }
  if( PB("nc") ){
    graphFlags |= TIMELINE_NOCOLOR;
    blob_appendf(&qp, "&nc");
  }
  pCfg = construct_diff_flags(diffType, &DCfg);
  if( DCfg.diffFlags & DIFF_IGNORE_ALLWS ){
    blob_appendf(&qp, "&w");
  }
  style_set_current_feature("vdiff");
  if( zBranch==0 ){
    style_submenu_element("Path", "%R/timeline?me=%T&you=%T", zFrom, zTo);
  }
  if( diffType!=0 ){

  if( zBranch==0 ){
    style_submenu_element("Invert","%R/vdiff?diff=%d&inv&%b", diffType, &qp);
  }
  if( zGlob ){
    style_submenu_element("Clear glob", "%R/vdiff?diff=%d&%b", diffType, &qp);
  }else{
    style_submenu_element("Patch", "%R/vpatch?from=%T&to=%T%s", zFrom, zTo,
           (DCfg.diffFlags & DIFF_IGNORE_ALLWS)?"&w":"");
  }
  if( diffType!=0 ){
    style_submenu_checkbox("w", "Ignore Whitespace", 0, 0);
  }
  if( zBranch ){
    style_header("Changes On Branch %h", zBranch);
  }else{

  }
  blob_reset(&qp);

  manifest_file_rewind(pFrom);
  pFileFrom = manifest_file_next(pFrom, 0);
  manifest_file_rewind(pTo);
  pFileTo = manifest_file_next(pTo, 0);
  DCfg.pRe = pRe;
  while( pFileFrom || pFileTo ){
    int cmp;
    if( pFileFrom==0 ){
      cmp = +1;
    }else if( pFileTo==0 ){
      cmp = -1;
    }else{
      cmp = fossil_strcmp(pFileFrom->zName, pFileTo->zName);
    }
    if( cmp<0 ){
      if( !zGlob || sqlite3_strglob(zGlob, pFileFrom->zName)==0 ){
        append_file_change_line(zFrom, pFileFrom->zName,
                                pFileFrom->zUuid, 0, 0, pCfg, 0);
      }
      pFileFrom = manifest_file_next(pFrom, 0);
    }else if( cmp>0 ){
      if( !zGlob || sqlite3_strglob(zGlob, pFileTo->zName)==0 ){
        append_file_change_line(zTo, pFileTo->zName,
                                0, pFileTo->zUuid, 0, pCfg,
                                manifest_file_mperm(pFileTo));
      }
      pFileTo = manifest_file_next(pTo, 0);
    }else if( fossil_strcmp(pFileFrom->zUuid, pFileTo->zUuid)==0 ){
      pFileFrom = manifest_file_next(pFrom, 0);
      pFileTo = manifest_file_next(pTo, 0);
    }else{
      if(!zGlob || (sqlite3_strglob(zGlob, pFileFrom->zName)==0
                || sqlite3_strglob(zGlob, pFileTo->zName)==0) ){
        append_file_change_line(zFrom, pFileFrom->zName,
                                pFileFrom->zUuid,
                                pFileTo->zUuid, 0, pCfg,
                                manifest_file_mperm(pFileTo));
      }
      pFileFrom = manifest_file_next(pFrom, 0);
      pFileTo = manifest_file_next(pTo, 0);
    }
  }
  manifest_destroy(pFrom);

  char *zV1;
  char *zV2;
  const char *zRe;
  ReCompiled *pRe = 0;
  u64 diffFlags;
  u32 objdescFlags = 0;
  int verbose = PB("verbose");
  DiffConfig DCfg;

  login_check_credentials();
  if( !g.perm.Read ){ login_needed(g.anon.Read); return; }
  diffType = preferred_diff_type();
  if( P("from") && P("to") ){
    v1 = artifact_from_ci_and_filename("from");
    v2 = artifact_from_ci_and_filename("to");

    DiffConfig DCfg;
    pOut = cgi_output_blob();
    cgi_set_content_type("text/plain");
    diffFlags = 4;
    content_get(v1, &c1);
    content_get(v2, &c2);
    diff_config_init(&DCfg, diffFlags);
    DCfg.pRe = pRe;
    text_diff(&c1, &c2, pOut, &DCfg);
    blob_reset(&c1);
    blob_reset(&c2);
    return;
  }

  zV1 = db_text(0, "SELECT uuid FROM blob WHERE rid=%d", v1);
  zV2 = db_text(0, "SELECT uuid FROM blob WHERE rid=%d", v2);
  construct_diff_flags(diffType, &DCfg);
  DCfg.diffFlags |= DIFF_HTML;

  style_set_current_feature("fdiff");
  style_header("Diff");
  style_submenu_checkbox("w", "Ignore Whitespace", 0, 0);
  if( diffType==2 ){
    style_submenu_element("Unified Diff", "%R/fdiff?v1=%T&v2=%T&diff=1",
                           P("v1"), P("v2"));

    object_description(v1, objdescFlags,0, 0);
    @ <h2>To Artifact %z(href("%R/artifact/%!S",zV2))[%S(zV2)]</a>:</h2>
    object_description(v2, objdescFlags,0, 0);
  }
  if( pRe ){
    @ <b>Only differences that match regular expression "%h(zRe)"
    @ are shown.</b>
    DCfg.pRe = pRe;
  }
  @ <hr />
  append_diff(zV1, zV2, &DCfg);
  append_diff_javascript(diffType);
  style_finish_page();
}

/*
** WEBPAGE: raw
** URL: /raw/ARTIFACTID

*/
cson_value * json_generate_diff(const char *zFrom, const char *zTo,
                                int nContext, char fSbs,
                                char fHtml){
  int fromid;
  int toid;
  int outLen;
  DiffConfig DCfg;
  Blob from = empty_blob, to = empty_blob, out = empty_blob;
  cson_value * rc = NULL;
  int flags = (DIFF_CONTEXT_MASK & nContext)
    | (fSbs ? DIFF_SIDEBYSIDE : 0)
    | (fHtml ? DIFF_HTML : 0);
  fromid = name_to_typed_rid(zFrom, "*");
  if(fromid<=0){
      json_set_err(FSL_JSON_E_UNRESOLVED_UUID,
                   "Could not resolve 'from' ID.");
      return NULL;
  }
  toid = name_to_typed_rid(zTo, "*");
  if(toid<=0){
      json_set_err(FSL_JSON_E_UNRESOLVED_UUID,
                   "Could not resolve 'to' ID.");
      return NULL;
  }
  content_get(fromid, &from);
  content_get(toid, &to);
  blob_zero(&out);
  diff_config_init(&DCfg, flags);
  text_diff(&from, &to, &out, &DCfg);
  blob_reset(&from);
  blob_reset(&to);
  outLen = blob_size(&out);
  if(outLen>=0){
    rc = cson_value_new_string(blob_buffer(&out),
                               (unsigned int)blob_size(&out));
  }

  char const * zV2 = NULL;
  cson_object * pay = NULL;
  int argPos = g.json.dispatchDepth;
  int r1 = 0, r2 = 0;
  Manifest * pW1 = NULL, *pW2 = NULL;
  Blob w1 = empty_blob, w2 = empty_blob, d = empty_blob;
  char const * zErrTag = NULL;
  DiffConfig DCfg;
  char * zUuid = NULL;
  if( !g.perm.Hyperlink ){
    json_set_err(FSL_JSON_E_DENIED,
                 "Requires 'h' permissions.");
    return NULL;
  }

    goto manifest;
  }

  blob_init(&w1, pW1->zWiki, -1);
  blob_zero(&w2);
  blob_init(&w2, pW2->zWiki, -1);
  blob_zero(&d);
  diff_config_init(&DCfg, DIFF_IGNORE_EOLWS | DIFF_STRIP_EOLCR);
  text_diff(&w1, &w2, &d, &DCfg);
  blob_reset(&w1);
  blob_reset(&w2);

  pay = cson_new_object();

  zUuid = json_wiki_get_uuid_for_rid( pW1->rid );
  cson_object_set(pay, "v1", json_new_string(zUuid) );

  int *aC1;              /* Changes from pPivot to pV1 */
  int *aC2;              /* Changes from pPivot to pV2 */
  int i1, i2;            /* Index into aC1[] and aC2[] */
  int nCpy, nDel, nIns;  /* Number of lines to copy, delete, or insert */
  int limit1, limit2;    /* Sizes of aC1[] and aC2[] */
  int nConflict = 0;     /* Number of merge conflicts seen so far */
  int useCrLf = 0;
  DiffConfig DCfg;

  blob_zero(pOut);         /* Merge results stored in pOut */
  
  /* If both pV1 and pV2 start with a UTF-8 byte-order-mark (BOM),
  ** keep it in the output. This should be secure enough not to cause
  ** unintended changes to the merged file and consistent with what
  ** users are using in their source files.

  ** and pPivot => pV2 (into aC2).  Each of the aC1 and aC2 arrays is
  ** an array of integer triples.  Within each triple, the first integer
  ** is the number of lines of text to copy directly from the pivot,
  ** the second integer is the number of lines of text to omit from the
  ** pivot, and the third integer is the number of lines of text that are
  ** inserted.  The edit array ends with a triple of 0,0,0.
  */
  diff_config_init(&DCfg, 0);
  aC1 = text_diff(pPivot, pV1, 0, &DCfg);
  aC2 = text_diff(pPivot, pV2, 0, &DCfg);
  if( aC1==0 || aC2==0 ){
    free(aC1);
    free(aC2);
    return -1;
  }

  blob_rewind(pV1);        /* Rewind inputs:  Needed to reconstruct output */

  }
  @ <hr />
  @ Baseline: \
  skin_emit_skin_selector("basis", zBasis, zDraft);
  @ <input type="submit" name="diff" value="Unified Diff" />
  @ <input type="submit" name="sbsdiff" value="Side-by-Side Diff" />
  if( P("diff")!=0 || P("sbsdiff")!=0 ){

    Blob from, to, out;
    DiffConfig DCfg;
    construct_diff_flags(1, &DCfg);
    DCfg.diffFlags |= DIFF_STRIP_EOLCR;
    if( P("sbsdiff")!=0 ) DCfg.diffFlags |= DIFF_SIDEBYSIDE;
    blob_init(&to, zContent, -1);
    blob_init(&from, skin_file_content(zBasis, zFile), -1);
    blob_zero(&out);
    DCfg.diffFlags |= DIFF_HTML | DIFF_NOTTOOBIG; 
    if( DCfg.diffFlags & DIFF_SIDEBYSIDE ){
      text_diff(&from, &to, &out, &DCfg);
      @ %s(blob_str(&out))
    }else{
      DCfg.diffFlags |= DIFF_LINENO;
      text_diff(&from, &to, &out, &DCfg);
      @ <pre class="udiff">
      @ %s(blob_str(&out))
      @ </pre>
    }
    blob_reset(&from);
    blob_reset(&to);
    blob_reset(&out);

*/
void wdiff_page(void){
  const char *zId;
  const char *zPid;
  Manifest *pW1, *pW2 = 0;
  int rid1, rid2, nextRid;
  Blob w1, w2, d;

  DiffConfig DCfg;

  login_check_credentials();
  if( !g.perm.RdWiki ){ login_needed(g.anon.RdWiki); return; }
  zId = P("id");
  if( zId==0 ){
    rid1 = atoi(PD("rid","0"));

  nextRid = wiki_next(wiki_tagid(pW1->zWikiTitle),pW1->rDate);
  if( nextRid ){
    style_submenu_element("Next", "%R/wdiff?rid=%d", nextRid);
  }
  style_set_current_feature("wiki");
  style_header("Changes To %s", pW1->zWikiTitle);
  blob_zero(&d);
  construct_diff_flags(1, &DCfg);
  DCfg.diffFlags |= DIFF_HTML | DIFF_LINENO;
  text_diff(&w2, &w1, &d, &DCfg);
  @ <pre class="udiff">
  @ %s(blob_str(&d))
  @ <pre>
  manifest_destroy(pW1);
  manifest_destroy(pW2);
  style_finish_page();
}