reinstalling local deb file is no downgrade

If we have a (e.g. locally built) deb file installed and do try to
install it again apt complained about this being a downgrade, but it
wasn't as it is the very same version… it was just confused into not
merging the versions together which looks like a downgrade then.

The same size assumption is usually good, but given that volatile files
are parsed last (even after the status file) the base assumption no
longer holds, but is easy to adept without actually changing anything in
practice.

apt-pkg/deb/deblistparser.cc

@@ -999,7 +999,7 @@ bool debListParser::SameVersion(unsigned short const Hash,		/*{{{*/
    // status file is parsed last, so the first version we encounter is
    // probably also the version we have downloaded
    unsigned long long const Size = Section.FindULL("Size");
-   if (Size != 0 && Size != Ver->Size)
+   if (Size != 0 && Ver->Size != 0 && Size != Ver->Size)
       return false;
    // available everywhere, but easier to check here than to include in VersionHash
    unsigned char MultiArch = ParseMultiArch(false);

test/integration/test-apt-get-install-deb

@@ -45,8 +45,10 @@ testsuccess aptget install ./incoming/foo_1.0_i386.deb -o Debug::pkgCacheGen=1
 testdpkginstalled 'foo:i386'
 testfailure aptget install incoming/foo_1.0_i386.deb -o Debug::pkgCacheGen=1
 cd downloaded
-testsuccess aptget install "$(readlink -f ../incoming/foo_1.0_i386.deb)" -o Debug::pkgCacheGen=1 -y --allow-downgrades
-testsuccess aptget install ../incoming/foo_1.0_i386.deb -o Debug::pkgCacheGen=1 -y --allow-downgrades
+testsuccess aptget install "$(readlink -f ../incoming/foo_1.0_i386.deb)" -o Debug::pkgCacheGen=1 -y --reinstall
+testfailure grep 'is already the newest version' ../rootdir/tmp/testsuccess.output
+testsuccess aptget install ../incoming/foo_1.0_i386.deb -o Debug::pkgCacheGen=1 -y --reinstall
+testfailure grep 'is already the newest version' ../rootdir/tmp/testsuccess.output
 cd ..
 
 testsuccessequal "Reading package lists...
@@ -109,13 +111,21 @@ testsuccess aptget install ./incoming/pkg-as-it-should-be_0_all.deb
 testsuccess aptget install ./incoming/pkg-leading-newline_0_all.deb
 testsuccess aptget install ./incoming/pkg-trailing-newline_0_all.deb
 
-# see if permission dropping is checked before usage
+testempty apt clean
 if [ "$(id -u)" = '0' ]; then
-	apt clean
+	# see if permission dropping is checked before usage
 	chmod 711 ./incoming
-	testsuccess aptget install -y --allow-downgrades ./incoming/pkg-as-it-should-be_0_all.deb
+	testsuccess aptget install -y ./incoming/pkg-as-it-should-be_0_all.deb --reinstall
+	testfailure grep 'is already the newest version' rootdir/tmp/testsuccess.output
 	chmod 710 ./incoming
-	testsuccesswithnotice aptget install -y --allow-downgrades ./incoming/pkg-as-it-should-be_0_all.deb
+	testsuccesswithnotice aptget install -y ./incoming/pkg-as-it-should-be_0_all.deb --reinstall
+	testfailure grep 'is already the newest version' rootdir/tmp/testsuccesswithnotice.output
 	chmod 700 ./incoming
-	testsuccesswithnotice aptget install -y --allow-downgrades ./incoming/pkg-as-it-should-be_0_all.deb
+	testsuccesswithnotice aptget install -y ./incoming/pkg-as-it-should-be_0_all.deb --reinstall
+	testfailure grep 'is already the newest version' rootdir/tmp/testsuccesswithnotice.output
+else
+	testsuccess aptget install -y ./incoming/pkg-as-it-should-be_0_all.deb --reinstall
+	testfailure grep 'is already the newest version' rootdir/tmp/testsuccess.output
 fi
+
+