Don't overwrite existing files with ;s.

Closes issue #914.

common/content/hints.js

@@ -746,6 +746,7 @@ var Hints = Module("hints", {
         this.modes = {};
         this.addMode(";", "Focus hint",                           buffer.closure.focusElement);
         this.addMode("?", "Show information for hint",            function (elem) buffer.showElementInfo(elem));
+        // TODO: allow for ! override to overwrite existing paths -- where? --djk
         this.addMode("s", "Save hint",                            function (elem) buffer.saveLink(elem, false));
         this.addMode("f", "Focus frame",                          function (elem) dactyl.focus(elem.ownerDocument.defaultView));
         this.addMode("F", "Focus frame or pseudo-frame",          buffer.closure.focusElement, isScrollable);

common/locale/en-US/messages.properties

@@ -207,6 +207,8 @@ io.eNotDir = Not a directory
 io.eNotDir-1 = Not a directory %S
 io.exists = File exists (add ! to override)
 io.exists-1 = File %S exists (add ! to override)
+# XXX
+io.existsNoOverride-1 = File %S exists
 io.noCommand-1 = Command not found: %S
 io.noPrevDir = E186: No previous directory
 io.noSuchDir-1 = E344: Can't find directory %S

common/modules/buffer.jsm

@@ -585,8 +585,9 @@ var Buffer = Module("Buffer", {
      * Saves a page link to disk.
      *
      * @param {HTMLAnchorElement} elem The page link to save.
+     * @param {boolean} overwrite If true, overwrite any existing file.
      */
-    saveLink: function saveLink(elem) {
+    saveLink: function saveLink(elem, overwrite) {
         let { completion, dactyl, io } = this.modules;
 
         let self = this;
@@ -604,6 +605,8 @@ var Buffer = Module("Buffer", {
                     if (file.exists() && file.isDirectory())
                         file.append(Buffer.getDefaultNames(elem)[0][0]);
 
+                    util.assert(!file.exists() || overwrite, _("io.existsNoOverride", file.path));
+
                     try {
                         if (!file.exists())
                             file.create(File.NORMAL_FILE_TYPE, octal(644));