Consider providing a net461 moniker in nuget package

[devlead]

As per resent guidance provided by @terrajobst on Twitter recently

Main take aways

If you want to consume .NET Standard 1.5+ from .NET Framework, I recommend to be on 4.7.2.
If you dual target for .NET Standard and .NET Framework, you’ll get the best of both worlds.

Issue as a library author is many assemblies has dropped the .NET Framework monikers, libgit2sharp included, which means if I have libgit2sharp as a dependency, I myself can't target 4.6.1.

Did a quick PoC win fork devlead/libgit2sharp/cf417d65a2e2d8192e9b2676794372575d6ae49a, things seems to build & test locally.

Basic changes I did

https://github.com/devlead/libgit2sharp/blob/cf417d65a2e2d8192e9b2676794372575d6ae49a/LibGit2Sharp/LibGit2Sharp.csproj#L4

    <TargetFrameworks>netstandard2.0;net461</TargetFrameworks>

https://github.com/devlead/libgit2sharp/blob/cf417d65a2e2d8192e9b2676794372575d6ae49a/LibGit2Sharp/LibGit2Sharp.csproj#L41-L43

 <ItemGroup Condition=" '$(TargetFramework)' == 'net461' ">
    <PackageReference Include="System.Runtime.InteropServices.RuntimeInformation" Version="4.3.0" PrivateAssets="none" />
  </ItemGroup>

If this is something you might consider, I'll happily send in this as a PR.

[bording]

This is something I've already been taking a look at doing.

As you've noticed, this currently requires a taking a dependency on a package, which isn't really something I want to do.

Instead, we'll want to work around the need for that package.

[devlead]

@bording not that many places System.Runtime.InteropServices.RuntimeInformation is used, did a quick attempt to pollyfill with pr #1606