Mount docker volume as the base git-repository (and skip git-clone)

I found Support for --volumes-from? and following the links like

But what I want is for the git repository rather than some prebuilt binaries as the codebase is too large to clone for every build.

I also noticed that the drone-git plugin would check the emptiness of the git folder (, so it seems possible to prepare the code repo, letting the drone-git plugin skip the git-clone step.

Is this a sane approach for my purpose?
How can I specify the mount point for code in the drone.yml and make drone mount it first before doing git-clone?

Have you seen the following documentation page?

It seems that you can provide a custom clone step, which you could make use of to provide the data from your other volume perhaps.

I’m sure someone else will be able to jump in with a more concrete example, perhaps this may be able to get your somewhere, though.

Yes, I have seen the page.

By ‘custom a clone step,’ do you mean to write a customized plugin?
I cannot find the configuration that fits my purpose in the documentation without resorting to writing my customized plugin.

Edit: found a similar question [Fixed] Big repo, how to save the git clone time?. Unfortunately, the depth=1 options is not helpful enough.