(GH-1) Add ability to reset the ScriptHost

[augustoproiete]

I took an initial stab at this one and ended up going back to my initial idea of having a method that allows the dev to reset the ScriptHost.

There are two scenarios I'm thinking:

Scenario 1: (Not covered by this PR) The host app is controlled by the Cake dev, and the app is aware that the code being run is a Cake script and knows about Cake.Bridge, so it could potentially use something like ExecuteScoped, etc.

Scenario 2: (This PR) The host app is not controlled by the Cake dev, and the app is not aware that it's running a Cake script (all it knows is how to run C# code, and because it's referencing Cake.Bridge, everything magically works).

The goal in both scenarios is the same: Run a Cake script multiple times in the same process. Example of a Cake Script that would work after this PR:

build.cake:

var target = Context.Argument("target", "Test");
var configuration = Context.Argument("configuration", "Release");

Task("Test")
    .Does(() =>
    {
        Context.Information($"Hello from App Host ({configuration})");
    });

RunTarget(target);

#if MYCAKEHOST
ResetScriptHost();
#endif

We expect that the host app defines a constant MYCAKEHOST which tells us that CakeBridge is loaded and therefore we can call this method, otherwise running the .cake script normally via dotnet cake and other runners would just ignore this instruction.

Let me know what you think.

This seemed the cleanest way to call into Cake.Bridge whilst still being able to run the same code via Cake, and without changing the original Cake script code too much.

---

Closes #1

[devlead]

LGTM 👍

[devlead]

@augustoproiete your changes have been merged, thanks for your contribution 👍

[devlead]

On NuGet now
https://www.nuget.org/packages/Cake.Bridge/0.0.16-alpha

[augustoproiete]

Awesome. Cheers @devlead ! this opens a very interesting door!

Just a small (but important) correction on my own sample script now that I had more coffee:

#if MYCAKEHOST
ResetScriptHost();
#endif

var target = Context.Argument("target", "Test");
var configuration = Context.Argument("configuration", "Release");

Task("Test")
    .Does(() =>
    {
        Context.Information($"Hello from App Host ({configuration})");
    });

RunTarget(target);

The reset needs to be at the top to make sure we always get a new host before anything else runs, otherwise an exception stops the execution flow and we're back to the original problem in #1 with the duplicate tasks.