Add:
[[projects]]
  name = "github.com/sdboyer/deptest"
  packages = ["."]
  revision = "ff2948a2ac8f538c4ecd55962e919d1e13e74baf"
  version = "v1.0.0"

[[projects]]
  name = "github.com/stuff/realthing"
  packages = ["."]
  revision = "1f02e52d6bac308da54ab84a234c58a98ca82347"
  version = "2.0.0"

Remove:
[[projects]]
  name = "github.com/stuff/placeholder"
  packages = ["."]
  revision = "6694017eeb4e20fd277b049bf29dba4895c97234"
  version = "2.0.0"

Modify:
[[projects]]
  branch = "- master"
  name = "github.com/foo/bar"
  packages = ["- placeholder","+ thing"]
  revision = "f24338400f072ef18125ae0fbe6b06fe6d1783e7 -> 2a3a211e171803acb82d1d5d42ceb53228f51751"
  source = "+ http://github.example.com/foo/bar"
  version = "+ 1.2.0"

