merge sources.list lines based on Release filename

Merging by URI means that having sources lines with different URI
methods results in 'strange' warning and error messages, which aren't
very friendly from a user point of view as not encoding the method in
the filename is effectivly an implementation detail.

Merging by filename removes these messages and makes everything "work"
even if it isn't working the way it is configured as the indexes aren't
acquired over the method given, but over the first method for this
release file (which argueably is an implementation detail stemming from
the filename encoding, too).

So either direction isn't perfectly "right", but personally I prefer
"magic" over strange error messages (and doing a full-circle detection
of this with its own messages which would need to be translated feels
like way too much effort for dubious gain).

Closes: 826944

apt-pkg/deb/debmetaindex.cc

@@ -80,20 +80,19 @@ std::string debReleaseIndex::MetaIndexFile(const char *Type) const
    return _config->FindDir("Dir::State::lists") +
       URItoFileName(MetaIndexURI(Type));
 }
-
-std::string debReleaseIndex::MetaIndexURI(const char *Type) const
+static std::string constructMetaIndexURI(std::string URI, std::string const &Dist, char const * const Type)
 {
-   std::string Res;
-
    if (Dist == "/")
-      Res = URI;
+      ;
    else if (Dist[Dist.size()-1] == '/')
-      Res = URI + Dist;
+      URI += Dist;
    else
-      Res = URI + "dists/" + Dist + "/";
-   
-   Res += Type;
-   return Res;
+      URI += "dists/" + Dist + "/";
+   return URI + Type;
+}
+std::string debReleaseIndex::MetaIndexURI(const char *Type) const
+{
+   return constructMetaIndexURI(URI, Dist, Type);
 }
 									/*}}}*/
 // ReleaseIndex Con- and Destructors					/*{{{*/
@@ -919,27 +918,30 @@ class APT_HIDDEN debSLTypeDebian : public pkgSourceList::Type		/*{{{*/
 			   std::string const &Dist, std::string const &Section,
 			   bool const &IsSrc, std::map<std::string, std::string> const &Options) const
    {
-      debReleaseIndex *Deb = NULL;
-      for (std::vector<metaIndex *>::const_iterator I = List.begin();
-	   I != List.end(); ++I)
+      debReleaseIndex * Deb = nullptr;
+      std::string const FileName = URItoFileName(constructMetaIndexURI(URI, Dist, "Release"));
+      for (auto const &I: List)
       {
 	 // We only worry about debian entries here
-	 if (strcmp((*I)->GetType(), "deb") != 0)
+	 if (strcmp(I->GetType(), "deb") != 0)
+	    continue;
+
+	 auto const D = dynamic_cast<debReleaseIndex*>(I);
+	 if (unlikely(D == nullptr))
 	    continue;
 
-	 /* This check insures that there will be only one Release file
+	 /* This check ensures that there will be only one Release file
 	    queued for all the Packages files and Sources files it
 	    corresponds to. */
-	 if ((*I)->GetURI() == URI && (*I)->GetDist() == Dist)
+	 if (URItoFileName(D->MetaIndexURI("Release")) == FileName)
 	 {
-	    Deb = dynamic_cast<debReleaseIndex*>(*I);
-	    if (Deb != NULL)
-	       break;
+	    Deb = D;
+	    break;
 	 }
       }
 
       // No currently created Release file indexes this entry, so we create a new one.
-      if (Deb == NULL)
+      if (Deb == nullptr)
       {
 	 Deb = new debReleaseIndex(URI, Dist);
 	 List.push_back(Deb);

test/integration/test-different-methods-for-same-source

@@ -0,0 +1,33 @@
+#!/bin/sh
+set -e
+
+TESTDIR="$(readlink -f "$(dirname "$0")")"
+. "$TESTDIR/framework"
+setupenvironment
+configarchitecture 'amd64'
+
+insertpackage 'stable' 'foo' 'all' '1'
+insertsource 'stable' 'foo' 'all' '1'
+setupaptarchive --no-update
+
+# install a slowed down file: otherwise its to fast to reproduce combining
+NEWMETHODS="$(readlink -f rootdir)/usr/lib/apt/methods"
+OLDMETHODS="$(readlink -f rootdir/usr/lib/apt/methods)"
+rm "$NEWMETHODS"
+mkdir "$NEWMETHODS"
+backupIFS="$IFS"
+IFS="$(printf "\n\b")"
+for METH in $(find "$OLDMETHODS" ! -type d); do
+	ln -s "$OLDMETHODS/$(basename "$METH")" "$NEWMETHODS"
+done
+IFS="$backupIFS"
+ln -s "${OLDMETHODS}/http" "${NEWMETHODS}/http-ng"
+
+changetowebserver
+sed -i -e 's# http:# http-ng:#' $(find rootdir/etc/apt/sources.list.d -name '*-deb-src.list')
+
+testsuccess apt update
+cp rootdir/tmp/testsuccess.output update.log
+# all requests are folded into the first Release file
+testsuccess grep ' http-ng://' update.log
+testfailure grep ' http://' update.log