New Package manager dependency errors

It is not completely clear to me how to manage dependencies in the new package manager. I have in the manifest of our package a dependency with a specific branch and version.

(PowerSystems) pkg> st -m
Project PowerSystems v0.1.0
    Status `Manifest.toml`
  [9e28174c] BinDeps v0.8.10
  [b99e7846] BinaryProvider v0.4.1
  [336ed68f] CSV v0.3.1
  [49dc2e85] Calculus v0.4.1
  [324d7699] CategoricalArrays v0.3.13
  [944b1d66] CodecZlib v0.5.0
  [bbf7d656] CommonSubexpressions v0.2.0
  [34da2185] Compat v1.0.1
  [a93c6f00] DataFrames v0.13.1
  [9a8bc11e] DataStreams v0.4.0
  [864edb3b] DataStructures v0.11.0
  [163ba53b] DiffResults v0.0.3
  [b552c78f] DiffRules v0.0.7
  [f6369f11] ForwardDiff v0.8.5
  [f4508453] InfoZIP v0.1.6
  [2030c09a] InfrastructureModels v0.0.9
  [7d512f48] InternedStrings v0.7.0
  [682c06a0] JSON v0.19.0
  [4076af6c] JuMP v0.18.2+ #master (
  [b8f27783] MathOptInterface v0.5.1
  [f28f55f0] Memento v0.9.0
  [e1d29d7a] Missings v0.2.10
  [77ba4419] NaNMath v0.3.2
  [4d1e1d77] Nullables v0.0.7
  [23a24fe6] PowerModels v0.7.0 #moi-julia-v0.7 (
  [3cdcf5f2] RecipesBase v0.5.0
  [189a3867] Reexport v0.2.0
  [a2af1166] SortingAlgorithms v0.3.1
  [276daf66] SpecialFunctions v0.7.0
  [90137ffa] StaticArrays v0.8.3
  [2913bbd2] StatsBase v0.25.0
  [cea106d9] Syslogs v0.2.0
  [9e3dc215] TimeSeries v0.12.0
  [3bb67fe8] TranscodingStreams v0.8.0
  [30578b45] URIParser v0.4.0
  [ea10d353] WeakRefStrings v0.5.2
  [a5390f91] ZipFile v0.7.0
  [2a0f44e3] Base64 
  [ade2ca70] Dates 
  [8bb1440f] DelimitedFiles 
  [8ba89e20] Distributed 
  [9fa8497b] Future 
  [b77e0a4c] InteractiveUtils 
  [76f85450] LibGit2 
  [8f399da3] Libdl 
  [37e2e46d] LinearAlgebra 
  [56ddb016] Logging 
  [d6f4376e] Markdown 
  [a63ad114] Mmap 
  [44cfe95a] Pkg 
  [de0858da] Printf 
  [3fa0cd96] REPL 
  [9a3f8284] Random 
  [ea8e919c] SHA 
  [9e88b42a] Serialization 
  [1a1011a3] SharedArrays 
  [6462fe0b] Sockets 
  [2f01184e] SparseArrays 
  [10745b16] Statistics 
  [8dfed614] Test 
  [cf7118a7] UUIDs 
  [4ec0a83e] Unicode 

One of the packages (PowerModels) has a branch where we have updated the repository to use the new package manager in the branch moi-julia-v0.7. However, when I run add PowerSystems#master it throws this error:

(v0.7) pkg> add PowerSystems#master
  Updating registry at `~/.julia/registries/General`
  Updating git-repo ``
   Cloning git-repo ``
  Updating git-repo ``
 Resolving package versions...
ERROR: Unsatisfiable requirements detected for package PowerModels [23a24fe6]:
 PowerModels [23a24fe6] log:
 ├─PowerModels [23a24fe6] has no known versions!
 └─restricted to versions * by PowerSystems [c512b964] — no versions left
   └─PowerSystems [c512b964] log:
     ├─possible versions are: 0.1.0 or uninstalled
     └─PowerSystems [c512b964] is fixed to version 0.1.0

If I add PowerModels#moi-julia-v0.7 and then add PowerModels#master then it works fine. It is my understanding that I shouldn’t need to run the first add if it is properly defined in the manifest file. Moreover, it throws an error about PowerModels not having a version. However, after add PowerModels#moi-julia-v0.7 I can run st -m and get the correct version.

The Manifest and Project files are in this repo