Install from local git repository located in a file system directory

Is it possible to use devtools::install_git() to install a package from a local git repository located in some file system directory on MS Windows?

The examples only demonstrate how to install from a web URL (e.g. install_git("git://github.com/hadley/stringr.git")).

From within a package loaded via RStudio and devtools (CTRL + SHFT + L) and under git version control (i.e., subdirectory .git exists) , I tried the following:

devtools::install_git(paste0("git://", getwd(), ".git"))

The function came back with this error:

Downloading git repo git://C:/Users/Thyson/Documents/path/to/package/packagename.git
Error in git2r::clone(x$url, bundle, progress = FALSE) : 
  Error in 'git2r_clone': Malformed URL 'git://C:/Users/Thyson/Documents/path/to/package/packagename.git'

So I’m guessing I just got the file system URL wrong?

Git Baby is a git and github fan, let's start git clone.