If you are running in the default Julia environment (that is, if you haven’t done
pkg> activate path/to/your/project, then you already have a Manifest and Project file, and you can find them in
/v1.0 if you’re using Julia 1.0).
If you want to preserve that global environment, I believe you can just copy those two files somewhere (preferrably somewhere under version control so you can track their changes in the future).
$ mkdir MyProject
$ cd myProject
# Copy the global environment into this project
$ cp ~/.julia/environments/v1.1/*.toml .
# Start Julia with this new environment
$ julia --project
# Make sure everything is working
(MyProject) pkg> test MyPackage
# Commit it
$ git init
$ git add Manifest.toml Project.toml
$ git commit -m "project works"