Add a .NET Core 3 target for the global tool

[clairernovotny]

Fixes #277

[clairernovotny]

This probably needs updates to the base Linux images to test the netcoreapp3 version. That said, the core libraries have not changed, it's just another publish output.

[clairernovotny]

Not sure what to do with the NPM packing error:

2018-12-15T19:00:27.5871500Z [19:00:27] 'setPackageVersion' errored after 1.33 s
2018-12-15T19:00:27.5871767Z [19:00:27] Error: Command failed: dotnet "D:\a\1\s\src\nerdbank-gitversioning.npm\out\nbgv.cli\tools\netcoreapp2.1\any\nbgv.dll" get-version --project "." --format json
2018-12-15T19:00:27.5871851Z 
2018-12-15T19:00:27.5871941Z Unhandled Exception: System.TypeInitializationException: The type initializer for 'LibGit2Sharp.Core.NativeMethods' threw an exception. ---> System.DllNotFoundException: Unable to load DLL 'git2-a904fc6' or one of its dependencies: The specified module could not be found. (Exception from HRESULT: 0x8007007E)
2018-12-15T19:00:27.5872015Z    at LibGit2Sharp.Core.NativeMethods.git_libgit2_init()
2018-12-15T19:00:27.5872345Z    at LibGit2Sharp.Core.NativeMethods.InitializeNativeLibrary()
2018-12-15T19:00:27.5872405Z    at LibGit2Sharp.Core.NativeMethods..cctor()
2018-12-15T19:00:27.5872477Z    --- End of inner exception stack trace ---
2018-12-15T19:00:27.5872538Z    at LibGit2Sharp.Core.NativeMethods.git_libgit2_opts(Int32 option, UInt32 level, String path)
2018-12-15T19:00:27.5872603Z    at LibGit2Sharp.GlobalSettings.SetConfigSearchPaths(ConfigurationLevel level, String[] paths)
2018-12-15T19:00:27.5872695Z    at Nerdbank.GitVersioning.GitExtensions.OpenGitRepo(String pathUnderGitRepo) in D:\a\1\s\src\NerdBank.GitVersioning\GitExtensions.cs:line 391
2018-12-15T19:00:27.5872771Z    at Nerdbank.GitVersioning.Tool.Program.OnGetVersionCommand(String projectPath, String format, String versionOrRef) in D:\a\1\s\src\nbgv\Program.cs:line 236
2018-12-15T19:00:27.5872859Z    at Nerdbank.GitVersioning.Tool.Program.Main(String[] args) in D:\a\1\s\src\nbgv\Program.cs:line 110
2018-12-15T19:00:27.5872912Z 
2018-12-15T19:00:27.5872962Z     at ChildProcess.exithandler (child_process.js:276:12)
2018-12-15T19:00:27.5873014Z     at emitTwo (events.js:126:13)
2018-12-15T19:00:27.5873083Z     at ChildProcess.emit (events.js:214:7)
2018-12-15T19:00:27.5873135Z     at maybeClose (internal/child_process.js:915:16)
2018-12-15T19:00:27.5873192Z     at Process.ChildProcess._handle.onexit (internal/child_process.js:209:5)
2018-12-15T19:00:27.6410000Z ##[error]Gulp failed with error: C:\npm\prefix\gulp.cmd failed with return code: 1
2018-12-15T19:00:27.6423750Z ##[section]Finishing: Build nerdbank-gitversioning NPM package

[AArnott]

hmmm... I'm not sure I'm ready to require a preview .NET Core SDK on every box in order to build nb.gv.

The problem this solves will only exist when people have .NET Core 3.0 SDK and not 2.1, right? If so, perhaps this is the right solution, but will cause problems in the short term without actually solving any short-term problems. How about we hold off on this PR until .NET Core 3.0 is stable, and therefore has a more reasonable chance of being the only SDK installed?

[clairernovotny]

Up to you of course, but this was actively biting me here: https://github.com/dotnet/reactive/blob/linux-tests/azure-pipelines.rx.yml#L115-L137

It's not even enough to currently install both SDK's, you have to use the tool before installing 3.0.

I had to install 2.2, use the tool, then install 3.0.

[AArnott]

Ouch. OK, I'll take the hit.

[AArnott]

For future reference, the SDK installer seems to be here: https://dotnet.microsoft.com/download/dotnet-core/3.0

[AArnott]

It's not even enough to currently install both SDK's, you have to use the tool before installing 3.0.

Now that I have .NET Core 3.0 SDK Preview installed, the nbgv tool I was using before still works. So I'm not sure why it wasn't working for you.

I'm a bit surprised that since dotnet.exe itself has a --roll-forward-on-no-candidate-fx switch that it wouldn't be available to dotnet CLI tools.

[clairernovotny]

The scenario is a bit more nuanced. It's with the local install done with the .NET Core Installer task on Pipelines, not a global install of the tool.

[clairernovotny]

It's also one where there is no other .NET Core 2.x globally, like in the Linux Agents

[AArnott]

That --roll-forward-on-no-candidate-fx switch appears to be totally busted. I just filed https://github.com/dotnet/cli/issues/10477

[AArnott]

Ya, I guess I still need to figure out that NPM failure though.

[AArnott]

BTW, isn't there some text file that dotnet CLI tools can include in their package to cause the runtime to be more willing to pick them up in the face of a version difference?

[clairernovotny]

I'm not sure @KathleenDollard?

[AArnott]

The NPM failure isn't reproing for me locally. That makes it a lot harder to debug. :(

[ctaggart]

This was fixed by #326.