feat: ship Nuke.Common MVP transition shim

[ChrisonSimtian]

Summary

A hand-written Nuke.Common package that subclasses the canonical Fallout.* types to give NUKE-era consumers a transition lifeline. Adds our GitHub Packages feed, bumps Nuke.Common, and a class Build : NukeBuild { [Parameter] ... [Secret] ... [Solution] ... [GitRepository] ... } compiles unchanged.

Closes the MVP scope of #47. Source-generator follow-up tracked in #69.

Coverage

Old (Nuke.Common)	New (Fallout.Common)	Mechanism
NukeBuild	FalloutBuild	Subclass
INukeBuild	IFalloutBuild	Sub-interface
[Parameter]	ParameterAttribute	Subclass with constructor mirroring
[Secret]	SecretAttribute	Subclass
[Solution] (Nuke.Common.ProjectModel)	SolutionAttribute	Subclass
[GitRepository] (Nuke.Common.Git)	GitRepositoryAttribute	Subclass

What's NOT in this MVP (in #69)

• Source generator for the ~150 remaining public types in Common, plus other shim packages
• CI attributes ([GitHubActions] etc.) — bridged enums (GitHubActionsImage) need source-generator-level work
• Target delegate — C# disallows cross-type delegate conversion; fallout-migrate handles the source rename
• Static helper classes (DotNetTasks etc.) — need method-by-method delegation; scale-only-with-generator

Packaging

The shim is IsPackable=false by default — keeps the standard release pipeline from trying to push Nuke.Common to nuget.org (matkoch owns that ID). Producing the nupkg for the GH-Packages-only publish:

dotnet pack src/Shims/Nuke.Common/Nuke.Common.csproj -p:PackShims=true

Verified: default dotnet pack skips this project; with -p:PackShims=true it produces Nuke.Common.10.2.20-*.nupkg.

A dedicated dual-publish target (Fallout.* → nuget.org, Nuke.* → GH Packages) is part of #69.

Tests

tests/Nuke.Common.Shim.Tests/SampleConsumerBuild.cs is a compile-only test mirroring a typical consumer Build.cs:

using Nuke.Common;
using Nuke.Common.Git;
using Nuke.Common.ProjectModel;

public abstract class SampleConsumerBuild : NukeBuild, INukeBuild
{
    [Parameter] readonly string Configuration;
    [Secret] readonly string NuGetApiKey;
    [Solution] readonly Fallout.Common.ProjectModel.Solution Solution;
    [Solution("path/to/explicit.slnx")] readonly Fallout.Common.ProjectModel.Solution ExplicitSolution;
    [GitRepository] readonly Fallout.Common.Git.GitRepository GitRepository;
}

If this file compiles, the shim covers what it claims to cover. Compiles cleanly.

Side-effect

StronglyTypedSolutionGeneratorTest.Test#Solution.g.verified.cs regenerated — the new projects (Nuke.Common, Nuke.Common.Shim.Tests) get strongly-typed accessors Solution.Nuke_Common and Solution.Nuke_Common_Shim_Tests.

Verification

• dotnet build src/Shims/Nuke.Common: 0 errors, 0 warnings
• dotnet build tests/Nuke.Common.Shim.Tests: 0 errors (sample consumer compiles)
• dotnet test fallout.slnx: 408 passed, 7 skipped, 0 failed
• dotnet pack -p:PackShims=true: produces a valid nupkg
• dotnet pack (default): correctly skips the shim

Test plan for reviewer

• CI green on ubuntu-latest
• On merge, release pipeline doesn't try to push Nuke.Common to nuget.org (default Pack excludes it)
• Manually pack with PackShims=true and confirm consumers can install from a local feed

🤖 Generated with Claude Code