reimplement and simplify mirror:// method

Embedding an entire acquire stack and HTTP logic in the mirror method
made it rather heavy weight and fragile. This reimplement goes the other
way by doing only the bare minimum in the method itself and instead
redirect the actual download of files to their proper methods.

The reimplementation drops the (in the real world) unused query-string
feature as it isn't really implementable in the new architecture.

1 files changed, 6 insertions, 19 deletions

diff --git a/apt-pkg/acquire-worker.cc b/apt-pkg/acquire-worker.cc
index 1b1f4dc4c..016aebdcd 100644
--- a/apt-pkg/acquire-worker.cc
+++ b/apt-pkg/acquire-worker.cc
@@ -308,6 +308,7 @@ bool pkgAcquire::Worker::RunMessages()
 
 	    std::string const NewURI = LookupTag(Message,"New-URI",URI.c_str());
             Itm->URI = NewURI;
+	    auto const AltUris = VectorizeString(LookupTag(Message, "Alternate-URIs"), '\n');
 
 	    ItemDone();
 
@@ -335,28 +336,14 @@ bool pkgAcquire::Worker::RunMessages()
 	       if (Log != nullptr)
 		  Log->Done(desc);
 
-	       // if we change site, treat it as a mirror change
-	       if (URI::SiteOnly(NewURI) != URI::SiteOnly(desc.URI))
-	       {
-		  auto const firstSpace = desc.Description.find(" ");
-		  if (firstSpace != std::string::npos)
-		  {
-		     std::string const OldSite = desc.Description.substr(0, firstSpace);
-		     if (likely(APT::String::Startswith(desc.URI, OldSite)))
-		     {
-			std::string const OldExtra = desc.URI.substr(OldSite.length() + 1);
-			if (likely(APT::String::Endswith(NewURI, OldExtra)))
-			{
-			   std::string const NewSite = NewURI.substr(0, NewURI.length() - OldExtra.length());
-			   Owner->UsedMirror = URI::ArchiveOnly(NewSite);
-			   desc.Description.replace(0, firstSpace, Owner->UsedMirror);
-			}
-		     }
-		  }
-	       }
+	       ChangeSiteIsMirrorChange(NewURI, desc, Owner);
 	       desc.URI = NewURI;
 	       if (isDoomedItem(Owner) == false)
+	       {
+		  for (auto alt = AltUris.crbegin(); alt != AltUris.crend(); ++alt)
+		     Owner->PushAlternativeURI(std::string(*alt), {}, false);
 		  OwnerQ->Owner->Enqueue(desc);
+	       }
 	    }
             break;
          }