cleanup pdiff support detection decision

Its a bit unclean to create an item just to let the item decide that it
can't do anything and let it fail, so instead we let the item creator
decide in all cases if patching should be attempted.

Also pulls a small trick to get the hashes for the current file without
calculating them by looking at the 'old' Release file if we have it.

Git-Dch: Ignore

apt-pkg/acquire-item.cc

@@ -925,24 +925,36 @@ void pkgAcqMetaBase::QueueIndexes(bool const verify)			/*{{{*/
         Target != IndexTargets->end();
         ++Target)
    {
-      if (verify == true && TransactionManager->MetaIndexParser->Exists((*Target)->MetaKey) == false)
+      bool trypdiff = _config->FindB("Acquire::PDiffs", true);
+      if (verify == true)
       {
-	 // optional target that we do not have in the Release file are skipped
-	 if ((*Target)->IsOptional())
-	    continue;
+	 if (TransactionManager->MetaIndexParser->Exists((*Target)->MetaKey) == false)
+	 {
+	    // optional targets that we do not have in the Release file are skipped
+	    if ((*Target)->IsOptional())
+	       continue;
 
-         Status = StatAuthError;
-         strprintf(ErrorText, _("Unable to find expected entry '%s' in Release file (Wrong sources.list entry or malformed file)"), (*Target)->MetaKey.c_str());
-         return;
+	    Status = StatAuthError;
+	    strprintf(ErrorText, _("Unable to find expected entry '%s' in Release file (Wrong sources.list entry or malformed file)"), (*Target)->MetaKey.c_str());
+	    return;
+	 }
+
+	 // check if we have patches available
+	 trypdiff &= TransactionManager->MetaIndexParser->Exists((*Target)->MetaKey + ".diff/Index");
       }
+      // if we have no file to patch, no point in trying
+      trypdiff &= RealFileExists(GetFinalFileNameFromURI((*Target)->URI));
 
-      /* Queue the Index file (Packages, Sources, Translation-$foo
-         (either diff or full packages files, depending
-         on the users option) - we also check if the PDiff Index file is listed
-         in the Meta-Index file. Ideal would be if pkgAcqDiffIndex would test this
-         instead, but passing the required info to it is to much hassle */
-      if(_config->FindB("Acquire::PDiffs",true) == true && (verify == false ||
-          TransactionManager->MetaIndexParser->Exists((*Target)->MetaKey + ".diff/Index") == true))
+      // no point in patching from local sources
+      if (trypdiff)
+      {
+	 std::string const proto = (*Target)->URI.substr(0, strlen("file:/"));
+	 if (proto == "file:/" || proto == "copy:/" || proto == "cdrom:")
+	    trypdiff = false;
+      }
+
+      // Queue the Index file (Packages, Sources, Translation-$foo, …)
+      if (trypdiff)
          new pkgAcqDiffIndex(Owner, TransactionManager, *Target);
       else
          new pkgAcqIndex(Owner, TransactionManager, *Target);
@@ -1477,26 +1489,7 @@ pkgAcqDiffIndex::pkgAcqDiffIndex(pkgAcquire * const Owner,
    if(Debug)
       std::clog << "pkgAcqDiffIndex: " << Desc.URI << std::endl;
 
-   // look for the current package file
-   CurrentPackagesFile = GetFinalFileNameFromURI(Target->URI);
-
-   // FIXME: this file:/ check is a hack to prevent fetching
-   //        from local sources. this is really silly, and
-   //        should be fixed cleanly as soon as possible
-   if(!FileExists(CurrentPackagesFile) || 
-      Desc.URI.substr(0,strlen("file:/")) == "file:/")
-   {
-      // we don't have a pkg file or we don't want to queue
-      Failed("No index file, local or canceld by user", NULL);
-      return;
-   }
-
-   if(Debug)
-      std::clog << "pkgAcqDiffIndex::pkgAcqDiffIndex(): "
-	 << CurrentPackagesFile << std::endl;
-
    QueueURI(Desc);
-
 }
 									/*}}}*/
 // AcqIndex::Custom600Headers - Insert custom request headers		/*{{{*/
@@ -1570,6 +1563,7 @@ bool pkgAcqDiffIndex::ParseDiffIndex(string const &IndexDiffFile)	/*{{{*/
       return false;
    }
 
+   std::string const CurrentPackagesFile = GetFinalFileNameFromURI(Target->URI);
    HashStringList const TargetFileHashes = GetExpectedHashesFor(Target->MetaKey);
    if (TargetFileHashes.usable() == false || ServerHashes != TargetFileHashes)
    {
@@ -1581,7 +1575,23 @@ bool pkgAcqDiffIndex::ParseDiffIndex(string const &IndexDiffFile)	/*{{{*/
       return false;
    }
 
-   if (ServerHashes.VerifyFile(CurrentPackagesFile) == true)
+   HashStringList LocalHashes;
+   // try avoiding calculating the hash here as this is costly
+   if (TransactionManager->LastMetaIndexParser != NULL)
+   {
+      indexRecords::checkSum * const R = TransactionManager->LastMetaIndexParser->Lookup(Target->MetaKey);
+      if (R != NULL)
+	 LocalHashes = R->Hashes;
+   }
+   if (LocalHashes.usable() == false)
+   {
+      FileFd fd(CurrentPackagesFile, FileFd::ReadOnly);
+      Hashes LocalHashesCalc(ServerHashes);
+      LocalHashesCalc.AddFD(fd);
+      LocalHashes = LocalHashesCalc.GetHashStringList();
+   }
+
+   if (ServerHashes == LocalHashes)
    {
       // we have the same sha1 as the server so we are done here
       if(Debug)
@@ -1590,14 +1600,9 @@ bool pkgAcqDiffIndex::ParseDiffIndex(string const &IndexDiffFile)	/*{{{*/
       return true;
    }
 
-   FileFd fd(CurrentPackagesFile, FileFd::ReadOnly);
-   Hashes LocalHashesCalc;
-   LocalHashesCalc.AddFD(fd);
-   HashStringList const LocalHashes = LocalHashesCalc.GetHashStringList();
-
    if(Debug)
       std::clog << "Server-Current: " << ServerHashes.find(NULL)->toStr() << " and we start at "
-	 << fd.Name() << " " << fd.FileSize() << " " << LocalHashes.find(NULL)->toStr() << std::endl;
+	 << CurrentPackagesFile << " " << LocalHashes.FileSize() << " " << LocalHashes.find(NULL)->toStr() << std::endl;
 
    // parse all of (provided) history
    vector<DiffInfo> available_patches;

apt-pkg/acquire-item.h

@@ -648,11 +648,6 @@ class APT_HIDDEN pkgAcqDiffIndex : public pkgAcqBaseIndex
    /** \brief If \b true, debugging information will be written to std::clog. */
    bool Debug;
 
-   /** \brief The index file which will be patched to generate the new
-    *  file.
-    */
-   std::string CurrentPackagesFile;
-
    /** \brief A description of the Packages file (stored in
     *  pkgAcquire::ItemDesc::Description).
     */