Support .nuspec <license> in addition to deprecated <licenseUrl>

[michael-buschbeck-ms]

Description

The <licenseUrl> .nuspec element has been deprecated since end-2018 and replaced by <license>. Current guidance on including a custom license with a NuGet package says to include the license as a file (.txt or .md) in the package itself and to reference it through a <license type="file"> element in the .nuspec file.

However, the "View License" button in the "Manage NuGet Packages" UI ignores the <license> tag and instead directs the user to the contents of the <licenseUrl> element, which (for backward compatibility) is auto-generated by NuGet to point to aka.ms/deprecateLicenseUrl, a generic landing page that instructs the user on how to manually find and extract the license file from the NuGet package.

Instead, the "View License" button should honor the <license type="file"> element if it's present and show the packaged license file to the user. (Going by Visual Studio's example it's not even essential to render Markdown nicely.)

Note that this currently isn't an issue for any NuGet packages downloaded directly from NuGet.org because NuGet.org's API returns a fabricated <d:LicenseUrl> pointing to the package's license page on NuGet.org itself (example).

• NuGet Package: e.g. Microsoft.MixedReality.SceneUnderstanding from a file share (not from NuGet.org directly)
• NuGetForUnity Version: 1.2.4
• Unity Version: 2018.4.6f1
• Operating System: Windows 10