workaround msbuild bug dotnet/msbuild#3268

fix nuget feed urls if needed (msbuild pass `http:/` instead of `http://`)

Author: enricosada

src/Paket.Bootstrapper.preview3/Paket.Bootstrapper.preview3.csproj

@@ -13,6 +13,7 @@
       NO_SYSTEMWEBPROXY;
       PAKET_BOOTSTRAP_AS_TOOL;
       PAKET_BOOTSTRAP_TO_DIR;
+      PAKET_BOOTSTRAP_WORKAROUND_MSBUILD_URLS;
       $(DefineConstants)
     </DefineConstants>
   </PropertyGroup>

src/Paket.Bootstrapper/ArgumentParser.cs

@@ -127,6 +127,20 @@ public static BootstrapperOptions ParseArgumentsAndConfigurations(IEnumerable<st
                 options.Verbosity = Verbosity.Trace;
             }
 
+#if PAKET_BOOTSTRAP_WORKAROUND_MSBUILD_URLS
+            if (!String.IsNullOrEmpty(options.DownloadArguments.NugetSource)) {
+                string url = options.DownloadArguments.NugetSource;
+                string fixedUrl;
+                if (url.StartsWith("http://") || url.StartsWith("https://")) {
+                    fixedUrl = url;
+                }
+                else {
+                    fixedUrl = url.Replace("http:/", "http://").Replace("https:/", "https://");
+                }
+                options.DownloadArguments.NugetSource = fixedUrl;
+            } 
+#endif
+
             return options;
         }