Get best match when using VersionRange

[glennawatson]

Hey there,

On ReactiveUI.Pharamacist we use the same version matching as the NuGet team use.

So they have a built in method called "GetBestMatch" and they grab the version information from the NuGet server.

https://github.com/reactiveui/Pharmacist/blob/master/src/Pharmacist.Core/NuGet/NuGetPackageHelper.cs

IReadOnlyCollection<LibraryRange> LibraryIdentities;

// Use the provided nuget package source, or use nuget.org
var sourceRepository = new SourceRepository(nugetSource ?? new PackageSource(DefaultNuGetSource), Providers);

var packages = await Task.WhenAll(LibraryIdentities.Select(x => GetBestMatch(x, sourceRepository, token))).ConfigureAwait(false);

/// <summary>
/// Gets the best matching PackageIdentity for the specified LibraryRange.
/// </summary>
/// <param name="identity">The library range to find the best patch for.</param>
/// <param name="sourceRepository">The source repository where to match.</param>
/// <param name="token">A optional cancellation token.</param>
/// <returns>The best matching PackageIdentity to the specified version range.</returns>
public static async Task<PackageIdentity> GetBestMatch(LibraryRange identity, SourceRepository sourceRepository, CancellationToken token)
{
    var findPackageResource = await sourceRepository.GetResourceAsync<FindPackageByIdResource>(token).ConfigureAwait(false);

    var versions = await findPackageResource.GetAllVersionsAsync(identity.Name, _sourceCacheContext, _logger, token).ConfigureAwait(false);

    var bestPackageVersion = versions?.FindBestMatch(identity.VersionRange, version => version);

    return new PackageIdentity(identity.Name, bestPackageVersion);
}

At the moment you are just using the "Min Version" which is not always correct.

[glennawatson]

Changed to mention that it should be using best version matching. At the moment the min is not a great match.