This is a quick & dirty solution. I wrote this mainly to quickly manage lua libraries for Love2d where most libraries require you to download the repo, then copy and paste a single file into your project.

I hated doing this so I wrote wrp instead.

Run wrp to install all of your dependencies, but otherwise:

Usage:
  wrp [flags]
  wrp [command]
Available Commands:
  add         add a new dependency to project
  help        Help about any command
  init        init config
  rm          rm a dependency from project
  update      update a dependency in project
  version     Print the version number of wrp
Flags:
  -h, --help   help for wrp

• Will download any git repo by url
• Check out a tag/branch/revision
• Pick out the files that you want
• Write them to a chosen destination folder
• Update wrp.yaml with pinned versions

• Dependency tree of any sort. It will not solve your version issues
• Nested manifests

Add a wrp.yaml file to your project that looks like the following:

destination: vnd # what folder you will put your dependencies in
dependencies:
  github.com/kikito/anim8: # github repo to fetch at a tag
    tag: v2.3.1
    pick: [anim8.lua] # files to save from that repo
  github.com/tanema/Moan.lua: # commit hash
    hash: 404923c672f76b82ec9dfead7077fa9f289be9bd
    pick: [Moan] # save a folder
  github.com/kikito/beholder.lua: # branch
    branch: demo

> git clone git@github.com:tanema/wrp.git
> cd wrp
> go install .