Godep has been pretty composable in my experience. I use Godep in a makefile to build, and it does everything in a constructed GOPATH as well.

  GOPATH := ${CURDIR}/build
  
  build:
    @env GOPATH="${GOPATH}" godep restore
    @test -d "${GOPATH}/src/github.com/user/repo" || ln -s "${CURDIR}" "${GOPATH}/src/github.com/user/repo"
    @env GOPATH="${GOPATH}" go install github.com/user/repo

I do like the look of Goop's dep format file though. The Godeps file is pretty ugly in comparison.