xmake init and force create project

[Bricklou]

Is your feature request related to a problem? Please describe.

I often work with already created or cloned projects where I want to initialize a xmake project (i.e. fresh created git repo with default README file). But at the moment, xmake doesn't allow creating projects in non-empty directories.

Describe the solution you'd like

1. Add an -f / --force to force xmake to create a project
2. Add a xmake init command to initialize a project in the current folder. Maybe add a prompt to confirm the action if there are files conflicts or if the directory is not empty.

[waruqi]

you can update to dev branch and try it.

xmake create -f -P . test
xmake create --force -P . test