Don't fail for multiple readme files in content

When multiple readme files exist in package content, but with distinct relative paths within it, our package inference would fail because it would consider only the FileName when updating its Pack properties.

Author: kzu

src/NuGetizer.Tasks/NuGetizer.Inference.targets

@@ -286,9 +286,9 @@ Copyright (c) .NET Foundation. All rights reserved.
 
     <!-- Even if all these conditions are false, the user can still explicitly pack the file, of course -->
     <ItemGroup Label="Readme" Condition="'$(PackReadme)' == 'true' and '$(PackageReadmeFile)' != '' and '$(IsPackable)' == 'true'">
-      <_ExistingReadme Include="@(None -> WithMetadataValue('Filename', '$(PackageReadmeFilename)'))" />
-      <_ExistingReadme Include="@(Content -> WithMetadataValue('Filename', '$(PackageReadmeFilename)'))" Condition="'@(_ExistingReadme)' == ''" />
-      <_ExistingReadme Include="$(MSBuildProjectDirectory)\$(PackageReadmeFilename)$(PackageReadmeExtension)" Condition="'@(_ExistingReadme)' == '' and Exists('$(MSBuildProjectDirectory)\$(PackageReadmeFilename)$(PackageReadmeExtension)')" />
+      <_ExistingReadme Include="@(None -> WithMetadataValue('Identity', '$(PackageReadmeFile)'))" />
+      <_ExistingReadme Include="@(Content -> WithMetadataValue('Identity', '$(PackageReadmeFile)'))" Condition="'@(_ExistingReadme)' == ''" />
+      <_ExistingReadme Include="$(MSBuildProjectDirectory)\$(PackageReadmeFile)" Condition="'@(_ExistingReadme)' == '' and Exists('$(MSBuildProjectDirectory)\$(PackageReadmeFile)')" />
 
       <InferenceCandidate Include="@(_ExistingReadme -> Distinct())"
                           PackagePath="%(Filename)%(Extension)"

src/NuGetizer.Tests/NuGetizer.Tests.csproj

@@ -3,7 +3,7 @@
   <PropertyGroup>
     <TargetFramework>net472</TargetFramework>
     <DefaultItemExcludes>$(DefaultItemExcludes);Scenarios\**\*</DefaultItemExcludes>
-    <LangVersion>Latest</LangVersion>
+    <LangVersion>Preview</LangVersion>
   </PropertyGroup>
 
   <ItemGroup>

src/NuGetizer.Tests/given_a_packaging_project.cs

@@ -437,6 +437,37 @@ public void when_readme_found_then_adds_metadata_and_content()
             }));
         }
 
+        [Fact]
+        public void when_multiple_readmes_found_then_adds_metadata_and_content_for_root()
+        {
+            var result = Builder.BuildProject(@"
+<Project Sdk='Microsoft.Build.NoTargets/3.7.0'>
+  <PropertyGroup>
+    <PackageId>Packer</PackageId>
+    <TargetFramework>net6.0</TargetFramework>
+    <!-- Only needed since for scenarios we set this to false. -->
+    <EnableDefaultItems>true</EnableDefaultItems>
+  </PropertyGroup>
+</Project>",
+                "Pack,GetPackageContents", output,
+                files: [("readme.md", @"# readme"), ("docs/readme.md", @"# readme2")]);
+
+            result.AssertSuccess(output);
+
+            // Assert the readme file is added to the package
+            Assert.Contains(result.Items, item => item.Matches(new
+            {
+                PackagePath = @"readme.md",
+            }));
+
+            // Assert the package metadata is present too
+            Assert.Contains(result.Items, item => item.Matches(new
+            {
+                Identity = "Packer",
+                Readme = "readme.md",
+            }));
+        }
+
         [Fact]
         public void when_readme_custom_extension_specified_then_adds_metadata_and_content()
         {