libcore|PackageFeed: Links to loaded packages use the package identifier

Don't link with the full name containing an extension. It's better to
be agnostic of the actual format that is implied by the extension.

doomsday/libcore/include/de/filesys/linkfile.h

@@ -80,7 +80,16 @@ class LinkFile : public File
     Node const *tryGetChild(String const &name) const;
 
 public:
-    static LinkFile *newLinkToFile(File const &file);
+    /**
+     * Creates a new link to an existing file.
+     *
+     * @param file      Target file.
+     * @param linkName  Name of the created link file. If empty, the target file's
+     *                  name is used as the link's name.
+     *
+     * @return New LinkFile instance. Caller gets ownership.
+     */
+    static LinkFile *newLinkToFile(File const &file, String linkName = "");
 
 private:
     DENG2_PRIVATE(d)

doomsday/libcore/src/filesys/linkfile.cpp

@@ -143,9 +143,12 @@ filesys::Node const *LinkFile::tryGetChild(String const &name) const
     return 0;
 }
 
-LinkFile *LinkFile::newLinkToFile(File const &file)
+LinkFile *LinkFile::newLinkToFile(File const &file, String linkName)
 {
-    LinkFile *link = new LinkFile(file.name());
+    // Fall back to using the target's name.
+    if(linkName.isEmpty()) linkName = file.name();
+
+    LinkFile *link = new LinkFile(linkName);
     link->setTarget(file);
     link->setStatus(file.status());
     return link;

doomsday/libcore/src/filesys/packagefeed.cpp

@@ -54,10 +54,10 @@ void PackageFeed::populate(Folder &folder)
     {
         Package *pkg = i.value();
 
-        if(folder.has(pkg->file().name())) continue; // Already there.
+        if(folder.has(i.key())) continue; // Already there.
 
         // Create a link to the loaded package's file.
-        LinkFile &link = folder.add(LinkFile::newLinkToFile(pkg->file()));
+        LinkFile &link = folder.add(LinkFile::newLinkToFile(pkg->file(), i.key()));
 
         // We will decide on pruning this.
         link.setOriginFeed(this);