SCM - Add an `actionButton` property to the SourceControl api

[eamodio]

Refs: #110882

This proposal adds a new actionButton property to the SourceControl object, to allow SCM extensions to contribute a large "cta" style button to a repository.

Here is the proposed api addition:

export interface SourceControl {
	actionButton?: Command;
}

This is currenty being used by the built-in Git extension to provide the "Publish Changes" or "Sync Changes" button when there are unpublished or unpushed commits.

[mattseddon]

@lszomoru is there any plan for this to become available in the stable API?

I'd like to use it in the DVC Extension for VS Code.

Use case is here: iterative/vscode-dvc#1769.

Some high level details about the extension can be found at microsoft/vscode-discussions#54.

[lszomoru]

@mattseddon, thanks for the interest in the Action Button. The last two milestones we evolved the shape of the property in order to accommodate the "Commit" action button. I think that soon we will reach a phase where we can look at finalising the API.

[DavidGoldman]

Any update on this becoming stable?

[lszomoru]

@DavidGoldman, no progress was made in finalising the action button. Sorry.