[Spec] release branching strategy for maui, xamarin-macios, and xamarin-android

Other .NET repos have branch names such as:

• https://github.com/dotnet/installer/tree/release/6.0.1xx-preview1
• https://github.com/dotnet/installer/tree/release/6.0.1xx-preview2

Starting with Preview 4, I think we should create a new 6.0.1xx-preview4 branch on:

• dotnet/maui
• xamarin/xamarin-macios
• xamarin/xamarin-android

Looking at the .NET 6 Schedule (private link), we would do this during the Release branch snap and build timeframe. We would do this after bumping to an appropriate Preview 4 build of the dotnet/sdk.

I think branching will be done manually by each team for now.

Versions

Right now we have versions such as:

• Android: 11.0.200-ci.main.148
• MacCatalyst: 14.3.100-ci.main.337
• iOS: 14.4.100-ci.main.1192

After branching, we can manually make a commit that changes these versions so they come out to:

• Android: 11.0.200-preview.4.148
• MacCatalyst: 14.3.100-preview.4.337
• iOS: 14.4.100-preview.4.1192

Maui appears to have appropriate versioning already. I would recommend bumping the version to preview.5 on main, once 6.0.1xx-preview4 is branched.

See our doc for details on versioning.

/cc @dalexsoto @jonpryor @Redth

[dalexsoto]

@jonathanpeppers looks good to me, please coordinate with either @rolfbjarne or @mandel-macaque for branching.

[rmarinho]

Just heads up we are going to make main do ci.main, and after we branch we will update GitInfo that commands the version numbers to be -preview4