file(DOWNLOAD): Make TLS options behave as documented

The logic added in commit e1c89f08 (file(DOWNLOAD): Add options for SSL,
2012-08-21) did not actually provide the documented behavior.  Simplify
the implementation to read the variable values first and then replace
them with the explicit argument values if encountered.  Always set the
curl option CURLOPT_SSL_VERIFYPEER to either on or off explicitly
instead of depending on the curl default behavior.

Source/cmFileCommand.cxx

@@ -2667,9 +2667,8 @@ cmFileCommand::HandleDownloadCommand(std::vector<std::string> const& args)
   long inactivity_timeout = 0;
   std::string verboseLog;
   std::string statusVar;
-  std::string caFile;
-  bool checkTLS = false;
-  bool verifyTLS = false;
+  bool tls_verify = this->Makefile->IsOn("CMAKE_TLS_VERIFY");
+  const char* cainfo = this->Makefile->GetDefinition("CMAKE_TLS_CAINFO");
   std::string expectedHash;
   std::string hashMatchMSG;
   cmsys::auto_ptr<cmCryptoHash> hash;
@@ -2728,8 +2727,7 @@ cmFileCommand::HandleDownloadCommand(std::vector<std::string> const& args)
       ++i;
       if(i != args.end())
         {
-        verifyTLS = cmSystemTools::IsOn(i->c_str());
-        checkTLS = true;
+        tls_verify = cmSystemTools::IsOn(i->c_str());
         }
       else
         {
@@ -2742,7 +2740,7 @@ cmFileCommand::HandleDownloadCommand(std::vector<std::string> const& args)
       ++i;
       if(i != args.end())
         {
-        caFile = *i;
+        cainfo = i->c_str();
         }
       else
         {
@@ -2866,37 +2864,19 @@ cmFileCommand::HandleDownloadCommand(std::vector<std::string> const& args)
   check_curl_result(res, "DOWNLOAD cannot set debug function: ");
 
   // check to see if TLS verification is requested
-  const char* verifyValue =
-    this->Makefile->GetDefinition("CMAKE_TLS_VERIFY");
-  // if there is a cmake variable or if the command has TLS_VERIFY requested
-  if(verifyValue || checkTLS)
+  if(tls_verify)
     {
-    // the args to the command come first
-    bool verify = verifyTLS;
-    if(!verify && verifyValue)
-      {
-      verify = cmSystemTools::IsOn(verifyValue);
-      }
-    if(verify)
-      {
-      res = ::curl_easy_setopt(curl, CURLOPT_SSL_VERIFYPEER, 1);
-      check_curl_result(res, "Unable to set TLS/SSL Verify on: ");
-      }
-    else
-      {
-      res = ::curl_easy_setopt(curl, CURLOPT_SSL_VERIFYPEER, 0);
-      check_curl_result(res, "Unable to set TLS/SSL Verify off: ");
-      }
+    res = ::curl_easy_setopt(curl, CURLOPT_SSL_VERIFYPEER, 1);
+    check_curl_result(res, "Unable to set TLS/SSL Verify on: ");
     }
-  // check to see if a CAINFO file has been specified
-  const char* cainfo =
-    this->Makefile->GetDefinition("CMAKE_TLS_CAINFO");
-  // command arg comes first
-  if(caFile.size())
+  else
     {
-    cainfo = caFile.c_str();
+    res = ::curl_easy_setopt(curl, CURLOPT_SSL_VERIFYPEER, 0);
+    check_curl_result(res, "Unable to set TLS/SSL Verify off: ");
     }
-  if(cainfo)
+  // check to see if a CAINFO file has been specified
+  // command arg comes first
+  if(cainfo && *cainfo)
     {
     res = ::curl_easy_setopt(curl, CURLOPT_CAINFO, cainfo);
     check_curl_result(res, "Unable to set TLS/SSL Verify CAINFO: ");