Evaluate supporting baseline in dotnet new and template engine

[vlada-shubina]

Currently template engine supports baseline: set of predefined input parameters that can be used when running or filtering templates.

dotnet new supports --baseline switch, but for now it is hidden.

Evaluate do we need this feature enabled for .NET 7, keep it hidden as is or should we remove it.

[baronfel]

Some open questions for me to investigate:

• Need to run down places where this feature is currently used - this should be easily doable from the search manifest
• Some code/design archeology to run down the history/driving use case of the feature

[baronfel]

Internal Usage:

• dotnet/templating - used to set the Framework parameter in the class library templates
• dotnet/aspnetcore - not used
• dotnet/winforms - not used
• dotnet/maui - not used

External Usage:

• Falanx.Templates
  • sets the Framework like the dotnet/templating templates do
• Dynamensions.Templates.Discord
  • sets the Framework like the dotnet/templating templates do
• ZTR.Utilities.Templates
  • sets the Framework like the dotnet/templating templates do
• RandomChance.Common.Templates
  • sets the Framework like the dotnet/templating templates do

All of the external usage feels very copy/pasted from our templates to me. This isn't surprising, given that we don't have a template-for-templates. I don't think that this functionality is very widely used at the moment. There is a potential use case for it as a solution to https://github.com/dotnet/templating/issues/3654, however.

[vlada-shubina]

No change to this behavior in scope of #2191, the baseline option remains hidden. Keeping the issue open for discussions.

[baronfel]

We should deprecate baseline - it's not widely used in the ecosystem and where it is used we have no evidence that template users actually use the baselines.

[vlada-shubina]

As it was agreed to deprecate baseline, we need to make all code that uses it obsolete. The action is purely refactoring, until obsolete code is agreed to be removed.

Consider removing --baseline option from CLI or make it obsolete.