Godot version:
3.2 alpha
Issue description:

The dropdown default value/placeholder is an option itself. Should be shown as a placeholder or not at all.
Steps to reproduce:
Minimal reproduction project:
Fresh Godot Project
I introduced this bug originally :P
I am creating an issue so I remember to fix this as soon as I get free, or if anyone is willing, they can probably have a go at it.
Looks like a simple UI bug
It would probably make sense to remove the placeholder option if at least one VCS is available. Just select the one that was first added to the list :slightly_smiling_face:
If no VCSes are found, an error dialog can be displayed instead.
FWIW I think the "If no VCSes are found, an error dialog can be displayed instead." approach leads to a pretty unfriendly first experience--particularly with the current level of documentation as mentioned in https://github.com/godotengine/godot-docs/issues/2838.
My thinking is it would be nice if the "Set Up Version Control" displayed the error message (perhaps also stating "No VCS plugin available" in the disabled pop-up control) and then documented or linked to documentation on how to add an addon.
Most helpful comment
It would probably make sense to remove the placeholder option if at least one VCS is available. Just select the one that was first added to the list :slightly_smiling_face:
If no VCSes are found, an error dialog can be displayed instead.