Update contributing guide and fix local tests.

- fpm is required to pass tests.
- apex/log package needs to be available.
- gpgSign git option needs to be disabled for test repo.
  This is an issue when a developer has set gpgSign to true in
  their global .gitconfig file.

CONTRIBUTING.md

@@ -12,11 +12,12 @@ Prerequisites are:
 * Build:
   * `make`
   * [Go 1.8+](http://golang.org/doc/install)
+  * [fpm](https://fpm.readthedocs.io/en/latest/installing.html)
 
 Clone `goreleaser` from source into `$GOPATH`:
 
 ```sh
-$ pkdir -p $GOPATH/src/github.com/github.com/goreleaser
+$ mkdir -p $GOPATH/src/github.com/github.com/goreleaser
 $ cd $_
 $ git clone git@github.com:goreleaser/goreleaser.git
 $ cd goreleaser

Gopkg.lock

@@ -100,6 +100,6 @@
 [solve-meta]
   analyzer-name = "dep"
   analyzer-version = 1
-  inputs-digest = "d3f68b6665e34ba913718b1ea7bbe0dbb185290b5209146133ca8d70615c09ac"
+  inputs-digest = "5aac2f70507156662f63f0938ce9730bed3895cc5c519ac97307b9c8004088fe"
   solver-name = "gps-cdcl"
   solver-version = 1

Gopkg.toml

@@ -99,3 +99,8 @@
 [[constraint]]
   branch = "v2"
   name = "gopkg.in/yaml.v2"
+
+[[constraint]]
+  branch = "master"
+  name = "github.com/apex/log"
+

goreleaserlib/goreleaser_test.go

@@ -166,6 +166,7 @@ func setup(t *testing.T) (current string, back func()) {
 	assert.NoError(os.Chdir(folder))
 	var gitCmds = [][]string{
 		{"init"},
+		{"config", "commit.gpgSign", "false"},
 		{"add", "-A"},
 		{"commit", "--allow-empty", "-m", "asdf"},
 		{"tag", "v0.0.1"},

pipeline/git/git_test.go

@@ -277,6 +277,8 @@ func gitInit(t *testing.T) {
 	out, err := git("init")
 	assert.NoError(err)
 	assert.Contains(out, "Initialized empty Git repository")
+	_, err = git("config", "commit.gpgSign", "false")
+	assert.NoError(err)
 }
 
 func gitCommit(t *testing.T, msg string) {