Normalize Signed-By values by removing trailing commas everywhere

This fixes comparisons where either the stored or the input string
have a trailing comma.

apt-pkg/deb/debmetaindex.cc

@@ -687,12 +687,19 @@ bool debReleaseIndex::SetSignedBy(std::string const &pSignedBy)
 	 std::stringstream os;
 	 std::copy(fingers.begin(), fingers.end(), std::ostream_iterator<std::string>(os, ","));
 	 SignedBy = os.str();
-	 while (SignedBy[SignedBy.size() - 1] == ',')
-	    SignedBy.resize(SignedBy.size() - 1);
       }
+      // Normalize the string: Remove trailing commas
+      while (SignedBy[SignedBy.size() - 1] == ',')
+	 SignedBy.resize(SignedBy.size() - 1);
+   }
+   else {
+      // Only compare normalized strings
+      auto pSignedByView = APT::StringView(pSignedBy);
+      while (pSignedByView[pSignedByView.size() - 1] == ',')
+	 pSignedByView = pSignedByView.substr(0, pSignedByView.size() - 1);
+      if (pSignedByView != SignedBy)
+	 return _error->Error(_("Conflicting values set for option %s regarding source %s %s: %s != %s"), "Signed-By", URI.c_str(), Dist.c_str(), SignedBy.c_str(), pSignedByView.to_string().c_str());
    }
-   else if (SignedBy != pSignedBy)
-      return _error->Error(_("Conflicting values set for option %s regarding source %s %s: %s != %s"), "Signed-By", URI.c_str(), Dist.c_str(), SignedBy.c_str(), pSignedBy.c_str());
    return true;
 }
 									/*}}}*/

test/integration/test-releasefile-verification-noflat

@@ -0,0 +1,25 @@
+#!/bin/sh
+set -e
+
+TESTDIR="$(readlink -f "$(dirname "$0")")"
+. "$TESTDIR/framework"
+
+setupenvironment
+configarchitecture "i386"
+
+export APT_DONT_SIGN='Release.gpg'
+insertpackage 'unstable' 'foo' 'i386' '1.0'
+setupaptarchive "now" "now + 1 year"
+changetowebserver
+
+SIXPACK="$(aptkey --keyring keys/joesixpack.pub finger | grep 'Key fingerprint' | cut -d'=' -f 2 | tr -d ' ')"
+
+testsuccess aptget update
+
+msgmsg 'Warm archive with signed-by' 'Joe Sixpack'
+sed -i "/^Valid-Until: / a\
+Signed-By: ${SIXPACK}" rootdir/var/lib/apt/lists/*Release
+touch -d 'now - 1 year' rootdir/var/lib/apt/lists/*Release
+testsuccessequal "Get:1 http://localhost:${APTHTTPPORT} unstable InRelease [$(stat -c '%s' 'aptarchive/dists/unstable/InRelease') B]
+Reading package lists..." aptget update
+testsuccess aptcache show foo