Added dependency tracking and pinning using the "dep" tool

- Added go2nix in order to make installation in deployments-repo easy
- Added shell.nix which has all necessary build tools and dep tools
- Updated README.md with procedures for building, update-pinning and creating a nix-derivation

.gitignore

@@ -5,3 +5,10 @@
 
 # Default binary output file name
 /morph
+
+# vendor cache dir
+/vendor
+
+# go2nix outfiles
+/default.nix
+/deps.nix

Gopkg.toml

@@ -0,0 +1,42 @@
+# Gopkg.toml example
+#
+# Refer to https://github.com/golang/dep/blob/master/docs/Gopkg.toml.md
+# for detailed Gopkg.toml documentation.
+#
+# required = ["github.com/user/thing/cmd/thing"]
+# ignored = ["github.com/user/project/pkgX", "bitbucket.org/user/project/pkgA/pkgY"]
+#
+# [[constraint]]
+#   name = "github.com/user/project"
+#   version = "1.0.0"
+#
+# [[constraint]]
+#   name = "github.com/user/project2"
+#   branch = "dev"
+#   source = "github.com/myfork/project2"
+#
+# [[override]]
+#   name = "github.com/x/y"
+#   version = "2.4.0"
+#
+# [prune]
+#   non-go = false
+#   go-tests = true
+#   unused-packages = true
+
+
+[[constraint]]
+  name = "github.com/gobwas/glob"
+  version = "0.2.3"
+
+[[constraint]]
+  branch = "master"
+  name = "golang.org/x/crypto"
+
+[[constraint]]
+  name = "gopkg.in/alecthomas/kingpin.v2"
+  version = "2.2.6"
+
+[prune]
+  go-tests = true
+  unused-packages = true

README.md

@@ -1 +1,40 @@
+
+## Nix shell
+
+All commands mentioned below is available in the nix-shell, if you run `nix-shell` with working dir = project root.
+
+## Go dependencies
+
+Run `dep ensure -vendor-only` to (re-)install pinned dependencies in vendor-dir
+
+Gopkg.toml specifies at which branch/tag each dependency is requested to be at.
+Gopkg.lock specifies a concrete revision each dependency is pinned at.
+
+If you want to bump dependencies to newest commit, run `dep ensure -update`, this will change Gopkg.lock, which has to be git-committed.
+
+If you make larger changes to the code base, you can delete both Gopkg.toml and Gopkg.lock and run `dep init` followed by `dep ensure` to create a fresh set of dependency tracking files. **don't forget to test** afterwards.
+
+## Assets
+
 Run `go-bindata -pkg assets -o assets/assets.go data/` after updating files from data/
+
+## Building the project with pinned dependencies
+
+$ `nix-shell`
+
+$ `dep ensure -vendor-only`
+
+$ `go build`
+
+*Your GOPATH must be set in your local environment, however /vendor is used exclusively for dependency resolution.*
+
+
+## Building a nix derivation
+
+$ `nix-shell`
+
+$ `dep ensure -vendor-only`
+
+$ `go2nix save`
+
+*Produces "default.nix" and "deps.nix" which can be copied to the deployments repo*

go2nix-deps.nix

@@ -0,0 +1,48 @@
+# This file was generated by https://github.com/kamilchm/go2nix v2.0-dev
+[
+  {
+    goPackagePath = "github.com/Masterminds/semver";
+    fetch = {
+      type = "git";
+      url = "https://github.com/Masterminds/semver";
+      rev = "517734cc7d6470c0d07130e40fd40bdeb9bcd3fd";
+      sha256 = "1625b5sxpmlz60jw67j1ljfcc09d4lhxg3z6gc4am8s2rrdgwij6";
+    };
+  }
+  {
+    goPackagePath = "github.com/Masterminds/vcs";
+    fetch = {
+      type = "git";
+      url = "https://github.com/Masterminds/vcs";
+      rev = "3084677c2c188840777bff30054f2b553729d329";
+      sha256 = "1062m73h0pp5d0574lf6px4jsjgywnsbkw50inxx3zal5r185ydm";
+    };
+  }
+  {
+    goPackagePath = "github.com/pelletier/go-buffruneio";
+    fetch = {
+      type = "git";
+      url = "https://github.com/pelletier/go-buffruneio";
+      rev = "c37440a7cf42ac63b919c752ca73a85067e05992";
+      sha256 = "0l83p1gg6g5mmhmxjisrhfimhbm71lwn1r2w7d6siwwqm9q08sd2";
+    };
+  }
+  {
+    goPackagePath = "github.com/pelletier/go-toml";
+    fetch = {
+      type = "git";
+      url = "https://github.com/pelletier/go-toml";
+      rev = "5ccdfb18c776b740aecaf085c4d9a2779199c279";
+      sha256 = "1jl44j58y62rhnwkzw3mvcj725gdyzs45pq4ga81qqxwqxs3czsq";
+    };
+  }
+  {
+    goPackagePath = "golang.org/x/tools";
+    fetch = {
+      type = "git";
+      url = "https://go.googlesource.com/tools";
+      rev = "e6cb469339aef5b7be0c89de730d5f3cc8e47e50";
+      sha256 = "16q3ibisbzq8rx4irhzl2lw4nwr62x9ryv446kgic8ww3p30rlf9";
+    };
+  }
+]

go2nix.nix

@@ -0,0 +1,25 @@
+# This file was generated by https://github.com/kamilchm/go2nix v2.0-dev
+{ pkgs, stdenv, buildGoPackage, fetchFromGitHub, ... }:
+with import <nixpkgs> {};
+
+buildGoPackage rec {
+  name = "go2nix-unstable-${version}";
+  version = "0.2-dev";
+
+  goPackagePath = "github.com/kamilchm/go2nix";
+  subPackages = [ "cmd/go2nix" ];
+
+  src = fetchFromGitHub {
+    owner = "kamilchm";
+    repo = "go2nix";
+    rev = "6cd52450c74f013a7e7c284526b3983dd918b070";
+    sha256 = "1bazkn7f5pydcqsvqg8yfx56h4162i2sya8q835ssc8bbp5y8as6";
+  };
+
+  goDeps = ./go2nix-deps.nix;
+
+  meta = {
+    homepage = "https://github.com/kamilchm/go2nix";
+    description = "Reproducible builds and development environment for Go";
+  };
+}

shell.nix

@@ -0,0 +1,17 @@
+{ pkgs ? (import <nixpkgs> {}) }:
+
+let
+  go2nix_v2 = pkgs.callPackage ./go2nix.nix {};
+in
+  # Change to mkShell once that hits stable!
+  pkgs.stdenv.mkDerivation {
+    name = "morph-build-env";
+
+    buildInputs = with pkgs; [
+      go2nix_v2
+      go-bindata
+      nix-prefetch-git
+      dep
+      bashInteractive
+    ];
+  }