From 9ff948cb5547a04f4c5d104d3893e488eb42e772 Mon Sep 17 00:00:00 2001
From: Anubhav Mishra <anubhavmishra@me.com>
Date: Sat, 1 Jul 2017 14:51:50 -0700
Subject: [PATCH] Project config (#56)

* first incomplete draft for project config and pre run refactor

* adding prerun and terraform 0.9 and above support

* partial review

* Changes from pull review. Fix approvals

* more clean up and refactor of terraform init and environment commands to support terraform 0.9.0 and above

* making apply similar to plan for appending extra arguments

* review

* missed apply executor changes and fixing tests
---
 cmd/server.go                                 |   5 +-
 prerun/pre_run.go                             |  79 ++++
 {server => prerun}/pre_run_test.go            |  36 +-
 server/apply_executor.go                      | 121 +++---
 server/atlantis_config_file.go                |  46 ---
 server/event_parser.go                        |  16 +-
 server/plan_executor.go                       | 100 +++--
 server/pre_run.go                             | 100 -----
 server/project_config.go                      |  88 +++++
 ...ig_file_test.go => project_config_test.go} |  54 ++-
 server/server.go                              |  46 ++-
 server/terraform_client.go                    | 119 +++---
 .../github.com/hashicorp/go-version/LICENSE   | 354 ++++++++++++++++++
 .../github.com/hashicorp/go-version/README.md |  65 ++++
 .../hashicorp/go-version/constraint.go        | 178 +++++++++
 .../hashicorp/go-version/version.go           | 322 ++++++++++++++++
 .../go-version/version_collection.go          |  17 +
 vendor/vendor.json                            |   6 +
 18 files changed, 1353 insertions(+), 399 deletions(-)
 create mode 100644 prerun/pre_run.go
 rename {server => prerun}/pre_run_test.go (55%)
 delete mode 100644 server/atlantis_config_file.go
 delete mode 100644 server/pre_run.go
 create mode 100644 server/project_config.go
 rename server/{atlantis_config_file_test.go => project_config_test.go} (63%)
 create mode 100644 vendor/github.com/hashicorp/go-version/LICENSE
 create mode 100644 vendor/github.com/hashicorp/go-version/README.md
 create mode 100644 vendor/github.com/hashicorp/go-version/constraint.go
 create mode 100644 vendor/github.com/hashicorp/go-version/version.go
 create mode 100644 vendor/github.com/hashicorp/go-version/version_collection.go

diff --git a/cmd/server.go b/cmd/server.go
index a82bb524e..bca8e1331 100644
--- a/cmd/server.go
+++ b/cmd/server.go
@@ -2,11 +2,12 @@ package cmd
 
 import (
 	"fmt"
+	"os"
+
 	"github.com/hootsuite/atlantis/server"
 	"github.com/pkg/errors"
 	"github.com/spf13/cobra"
 	"github.com/spf13/viper"
-	"os"
 )
 
 // To add a new flag you must
@@ -179,7 +180,7 @@ Config values are overridden by environment variables which in turn are overridd
 		// config looks good, start the server
 		server, err := server.NewServer(config)
 		if err != nil {
-			return errors.Wrap(err, "Failed to initialize server")
+			return errors.Wrap(err, "initializing server")
 		}
 		return server.Start()
 	},
diff --git a/prerun/pre_run.go b/prerun/pre_run.go
new file mode 100644
index 000000000..718169ecb
--- /dev/null
+++ b/prerun/pre_run.go
@@ -0,0 +1,79 @@
+package prerun
+
+import (
+	"bufio"
+	"fmt"
+	"io/ioutil"
+	"os"
+	"os/exec"
+	"strings"
+
+	version "github.com/hashicorp/go-version"
+	"github.com/pkg/errors"
+)
+
+const InlineShebang = "/bin/sh -e"
+
+type PreRun struct{}
+
+// Start is the function that starts the pre run
+func (p *PreRun) Start(commands []string, path string, environment string, terraformVersion *version.Version) (string, error) {
+	// we create a script from the commands provided
+	if len(commands) == 0 {
+		return "", errors.New("prerun commands cannot be empty")
+	}
+
+	s, err := createScript(commands)
+
+	if err != nil {
+		return "", err
+	}
+
+	defer os.Remove(s)
+	// set environment variable for the run.
+	// this is to support scripts to use the ENVIRONMENT, ATLANTIS_TERRAFORM_VERSION
+	// and WORKSPACE variables in their scripts
+	os.Setenv("ENVIRONMENT", environment)
+	os.Setenv("ATLANTIS_TERRAFORM_VERSION", terraformVersion.String())
+	os.Setenv("WORKSPACE", path)
+	return execute(s)
+}
+
+func createScript(cmds []string) (string, error) {
+	tmp, err := ioutil.TempFile("/tmp", "atlantis-temp-script")
+	if err != nil {
+		return "", errors.Wrap(err, "preparing pre run shell script")
+	}
+
+	scriptName := tmp.Name()
+
+	// Write our contents to it
+	writer := bufio.NewWriter(tmp)
+	writer.WriteString(fmt.Sprintf("#!%s\n", InlineShebang))
+	cmdsJoined := strings.Join(cmds, "\n")
+	if _, err := writer.WriteString(cmdsJoined); err != nil {
+		return "", errors.Wrap(err, "preparing pre run")
+	}
+
+	if err := writer.Flush(); err != nil {
+		return "", errors.Wrap(err, "flushing contents to file")
+	}
+	tmp.Close()
+
+	if err := os.Chmod(scriptName, 0755); err != nil {
+		return "", errors.Wrap(err, "making pre run script executable")
+	}
+
+	return scriptName, nil
+}
+
+func execute(script string) (string, error) {
+	localCmd := exec.Command("sh", "-c", script)
+	out, err := localCmd.CombinedOutput()
+	output := string(out)
+	if err != nil {
+		return output, errors.Wrapf(err, "running script %s: %s", script, output)
+	}
+
+	return output, nil
+}
diff --git a/server/pre_run_test.go b/prerun/pre_run_test.go
similarity index 55%
rename from server/pre_run_test.go
rename to prerun/pre_run_test.go
index 3eb6313fb..2c0e748f9 100644
--- a/server/pre_run_test.go
+++ b/prerun/pre_run_test.go
@@ -1,11 +1,13 @@
-package server
+package prerun
 
 import (
-	"github.com/hootsuite/atlantis/logging"
-	. "github.com/hootsuite/atlantis/testing_util"
 	"log"
 	"os"
 	"testing"
+
+	version "github.com/hashicorp/go-version"
+	"github.com/hootsuite/atlantis/logging"
+	. "github.com/hootsuite/atlantis/testing_util"
 )
 
 var level logging.LogLevel = logging.Info
@@ -15,11 +17,7 @@ var logger = &logging.SimpleLogger{
 	Level:  level,
 }
 
-func TestPreRunCreateScript_empty(t *testing.T) {
-	scriptName, err := createScript(nil)
-	Assert(t, scriptName == "", "there should not be a script name")
-	Assert(t, err == nil, "there should not be an error")
-}
+var preRun = &PreRun{}
 
 func TestPreRunCreateScript_valid(t *testing.T) {
 	cmds := []string{"echo", "date"}
@@ -45,23 +43,7 @@ func TestPreRunExecuteScript_valid(t *testing.T) {
 
 func TestPreRun_valid(t *testing.T) {
 	cmds := []string{"echo", "date"}
-	prePlan := PrePlan{Commands: cmds}
-	preApply := PreApply{Commands: cmds}
-	var config Config
-	config.PrePlan = prePlan
-	config.PreApply = preApply
-	config.StashPath = "/some/path"
-	err := PreRun(&config, logger, "/some/path", &Command{environment: "staging", commandType: Plan})
-	Assert(t, err == nil, "should not error")
-
-}
-
-func TestPreRun_partial_valid(t *testing.T) {
-	cmds := []string{"echo", "date"}
-	prePlan := PrePlan{Commands: cmds}
-	var config Config
-	config.PrePlan = prePlan
-	config.StashPath = "/some/path"
-	err := PreRun(&config, logger, "/some/path", &Command{environment: "staging", commandType: Plan})
-	Assert(t, err == nil, "should not error")
+	version, _ := version.NewVersion("0.8.8")
+	_, err := preRun.Start(cmds, "/tmp/atlantis", "staging", version)
+	Ok(t, err)
 }
diff --git a/server/apply_executor.go b/server/apply_executor.go
index c64765af7..60938a913 100644
--- a/server/apply_executor.go
+++ b/server/apply_executor.go
@@ -1,17 +1,20 @@
 package server
 
 import (
-	"errors"
 	"fmt"
 	"os"
 	"strings"
 
+	"github.com/pkg/errors"
+
 	"path/filepath"
 
 	"strconv"
 
+	version "github.com/hashicorp/go-version"
 	"github.com/hootsuite/atlantis/locking"
 	"github.com/hootsuite/atlantis/plan"
+	"github.com/hootsuite/atlantis/prerun"
 )
 
 type ApplyExecutor struct {
@@ -25,6 +28,8 @@ type ApplyExecutor struct {
 	lockingClient         *locking.Client
 	requireApproval       bool
 	planBackend           plan.Backend
+	preRun                *prerun.PreRun
+	configReader          *ConfigReader
 }
 
 /** Result Types **/
@@ -67,8 +72,10 @@ func (a *ApplyExecutor) execute(ctx *CommandContext, github *GithubClient) {
 }
 
 func (a *ApplyExecutor) setupAndApply(ctx *CommandContext) ExecutionResult {
-	if approved, res := a.isApproved(ctx); !approved {
-		return res
+	if a.requireApproval {
+		if approved, res := a.isApproved(ctx); !approved {
+			return res
+		}
 	}
 
 	// todo: reclone repo and switch branch, don't assume it's already there
@@ -99,13 +106,28 @@ func (a *ApplyExecutor) setupAndApply(ctx *CommandContext) ExecutionResult {
 }
 
 func (a *ApplyExecutor) apply(ctx *CommandContext, repoDir string, plan plan.Plan) PathResult {
-	var config Config
-	var remoteStatePath string
+	tfEnv := ctx.Command.environment
+	lockAttempt, err := a.lockingClient.TryLock(plan.Project, tfEnv, ctx.Pull, ctx.User)
+	if err != nil {
+		return PathResult{
+			Status: Error,
+			Result: GeneralError{errors.Wrap(err, "trying acquire lock")},
+		}
+	}
+	if lockAttempt.LockAcquired != true && lockAttempt.CurrLock.Pull.Num != ctx.Pull.Num {
+		return PathResult{
+			Status: Error,
+			Result: GeneralError{fmt.Errorf("failed to acquire lock: lock held by pull request #%d", lockAttempt.CurrLock.Pull.Num)},
+		}
+	}
+
 	// check if config file is found, if not we continue the run
 	projectAbsolutePath := filepath.Dir(plan.LocalPath)
-	if config.Exists(projectAbsolutePath) {
+	var terraformApplyExtraArgs []string
+	var config ProjectConfig
+	if a.configReader.Exists(projectAbsolutePath) {
 		ctx.Log.Info("Config file found in %s", projectAbsolutePath)
-		err := config.Read(projectAbsolutePath)
+		config, err := a.configReader.Read(projectAbsolutePath)
 		if err != nil {
 			msg := fmt.Sprintf("Error reading config file: %v", err)
 			ctx.Log.Err(msg)
@@ -114,8 +136,34 @@ func (a *ApplyExecutor) apply(ctx *CommandContext, repoDir string, plan plan.Pla
 				Result: GeneralError{errors.New(msg)},
 			}
 		}
-		// need to use the remote state path and backend to do remote configure
-		err = PreRun(&config, ctx.Log, projectAbsolutePath, ctx.Command)
+
+		// add terraform arguments from project config
+		terraformApplyExtraArgs = config.GetExtraArguments(ctx.Command.commandType.String())
+	}
+
+	// check if terraform version is >= 0.9.0
+	terraformVersion := a.terraform.Version()
+	if config.TerraformVersion != nil {
+		terraformVersion = config.TerraformVersion
+	}
+	constraints, _ := version.NewConstraint(">= 0.9.0")
+	if constraints.Check(terraformVersion) {
+		// run terraform init and environment
+		outputs, err := a.terraform.RunTerraformInitAndEnv(projectAbsolutePath, tfEnv, config)
+		if err != nil {
+			msg := fmt.Sprintf("terraform init and environment commands failed. %s %v", outputs, err)
+			ctx.Log.Err(msg)
+			return PathResult{
+				Status: Error,
+				Result: GeneralError{errors.New(msg)},
+			}
+		}
+		ctx.Log.Info("terraform init and environment commands ran successfully %s", outputs)
+	}
+
+	// if there are pre plan commands then run them
+	if len(config.PrePlan.Commands) > 0 {
+		preRunOutput, err := a.preRun.Start(config.PreApply.Commands, projectAbsolutePath, ctx.Command.environment, config.TerraformVersion)
 		if err != nil {
 			msg := fmt.Sprintf("pre run failed: %v", err)
 			ctx.Log.Err(msg)
@@ -124,51 +172,7 @@ func (a *ApplyExecutor) apply(ctx *CommandContext, repoDir string, plan plan.Pla
 				Result: GeneralError{errors.New(msg)},
 			}
 		}
-		// check if terraform version is specified in config
-		if config.TerraformVersion != "" {
-			a.terraform.tfExecutableName = "terraform" + config.TerraformVersion
-		} else {
-			a.terraform.tfExecutableName = "terraform"
-		}
-	}
-
-	// NOTE: THIS CODE IS TO SUPPORT TERRAFORM PROJECTS THAT AREN'T USING ATLANTIS CONFIG FILE.
-	if config.StashPath == "" {
-		// configure remote state
-		statePath, err := a.terraform.ConfigureRemoteState(ctx.Log, repoDir, plan.Project, ctx.Command.environment, a.sshKey)
-		if err != nil {
-			msg := fmt.Sprintf("failed to set up remote state: %v", err)
-			ctx.Log.Err(msg)
-			return PathResult{
-				Status: Error,
-				Result: GeneralError{errors.New(msg)},
-			}
-		}
-		remoteStatePath = statePath
-	} else {
-		// use state path from config file
-		remoteStatePath = generateStatePath(config.StashPath, ctx.Command.environment)
-	}
-
-	if remoteStatePath != "" {
-		tfEnv := ctx.Command.environment
-		if tfEnv == "" {
-			tfEnv = "default"
-		}
-
-		lockAttempt, err := a.lockingClient.TryLock(plan.Project, tfEnv, ctx.Pull, ctx.User)
-		if err != nil {
-			return PathResult{
-				Status: Error,
-				Result: GeneralError{fmt.Errorf("failed to acquire lock: %s", err)},
-			}
-		}
-		if lockAttempt.LockAcquired != true && lockAttempt.CurrLock.Pull.Num != ctx.Pull.Num {
-			return PathResult{
-				Status: Error,
-				Result: GeneralError{fmt.Errorf("failed to acquire lock: lock held by pull request #%d", lockAttempt.CurrLock.Pull.Num)},
-			}
-		}
+		ctx.Log.Info("Pre run output: \n%s", preRunOutput)
 	}
 
 	// need to get auth data from assumed role
@@ -194,7 +198,10 @@ func (a *ApplyExecutor) apply(ctx *CommandContext, repoDir string, plan plan.Pla
 	}
 
 	ctx.Log.Info("running apply from %q", plan.Project.Path)
-	terraformApplyCmdArgs, output, err := a.terraform.RunTerraformCommand(projectAbsolutePath, []string{"apply", "-no-color", plan.LocalPath}, []string{
+	tfApplyCmd := []string{"apply", "-no-color", plan.LocalPath}
+	// append terraform arguments from config file
+	tfApplyCmd = append(tfApplyCmd, terraformApplyExtraArgs...)
+	terraformApplyCmdArgs, output, err := a.terraform.RunTerraformCommand(projectAbsolutePath, tfApplyCmd, []string{
 		fmt.Sprintf("AWS_ACCESS_KEY_ID=%s", credVals.AccessKeyID),
 		fmt.Sprintf("AWS_SECRET_ACCESS_KEY=%s", credVals.SecretAccessKey),
 		fmt.Sprintf("AWS_SESSION_TOKEN=%s", credVals.SessionToken),
@@ -219,10 +226,6 @@ func (a *ApplyExecutor) apply(ctx *CommandContext, repoDir string, plan plan.Pla
 }
 
 func (a *ApplyExecutor) isApproved(ctx *CommandContext) (bool, ExecutionResult) {
-	if !a.requireApproval {
-		return false, ExecutionResult{}
-	}
-
 	ok, err := a.github.PullIsApproved(ctx.Repo, ctx.Pull)
 	if err != nil {
 		msg := fmt.Sprintf("failed to determine if pull request was approved: %v", err)
diff --git a/server/atlantis_config_file.go b/server/atlantis_config_file.go
deleted file mode 100644
index 83d988bf3..000000000
--- a/server/atlantis_config_file.go
+++ /dev/null
@@ -1,46 +0,0 @@
-package server
-
-import (
-	"fmt"
-	"io/ioutil"
-	"os"
-	"path/filepath"
-
-	yaml "gopkg.in/yaml.v2"
-)
-
-const AtlantisConfigFile = "atlantis.yaml"
-
-type PrePlan struct {
-	Commands []string `yaml:"commands"`
-}
-
-type PreApply struct {
-	Commands []string `yaml:"commands"`
-}
-
-type Config struct {
-	PrePlan          PrePlan  `yaml:"pre_plan"`
-	PreApply         PreApply `yaml:"pre_apply"`
-	StashPath        string   `yaml:"stash_path"`
-	TerraformVersion string   `yaml:"terraform_version"`
-}
-
-func (c *Config) Exists(execPath string) bool {
-	// Check if config file exists
-	_, err := os.Stat(filepath.Join(execPath, AtlantisConfigFile))
-	return err == nil
-}
-
-func (c *Config) Read(execPath string) error {
-	raw, err := ioutil.ReadFile(filepath.Join(execPath, AtlantisConfigFile))
-	if err != nil {
-		return fmt.Errorf("Couldn't read atlantis config file %q: %v", execPath, err)
-	}
-
-	if err := yaml.Unmarshal(raw, &c); err != nil {
-		return fmt.Errorf("Couldn't decode yaml in atlantis config file %q: %v", execPath, err)
-	}
-
-	return nil
-}
diff --git a/server/event_parser.go b/server/event_parser.go
index 523b0082f..0c61d352b 100644
--- a/server/event_parser.go
+++ b/server/event_parser.go
@@ -3,9 +3,10 @@ package server
 import (
 	"errors"
 	"fmt"
+	"regexp"
+
 	"github.com/google/go-github/github"
 	"github.com/hootsuite/atlantis/models"
-	"regexp"
 )
 
 type EventParser struct{}
@@ -34,7 +35,12 @@ func (e *EventParser) DetermineCommand(comment *github.IssueCommentEvent) (*Comm
 	if match[4] == "--verbose" {
 		verbose = true
 	}
-	command := &Command{verbose: verbose, environment: match[3]}
+	// defaulting to terraform's default environment
+	env := "default"
+	if match[3] != "" {
+		env = match[3]
+	}
+	command := &Command{verbose: verbose, environment: env}
 	switch match[1] {
 	case "plan":
 		command.commandType = Plan
@@ -134,9 +140,9 @@ func (e *EventParser) ExtractRepoData(ghRepo *github.Repository) (models.Repo, e
 		return repo, errors.New("repository.ssh_url is null")
 	}
 	return models.Repo{
-		Owner: repoOwner,
+		Owner:    repoOwner,
 		FullName: repoFullName,
-		SSHURL: repoSSHURL,
-		Name: repoName,
+		SSHURL:   repoSSHURL,
+		Name:     repoName,
 	}, nil
 }
diff --git a/server/plan_executor.go b/server/plan_executor.go
index d5d84bbb9..6c3ec71e3 100644
--- a/server/plan_executor.go
+++ b/server/plan_executor.go
@@ -9,10 +9,12 @@ import (
 	"path/filepath"
 	"strings"
 
+	version "github.com/hashicorp/go-version"
 	"github.com/hootsuite/atlantis/locking"
 	"github.com/hootsuite/atlantis/logging"
 	"github.com/hootsuite/atlantis/models"
 	"github.com/hootsuite/atlantis/plan"
+	"github.com/hootsuite/atlantis/prerun"
 	"github.com/pkg/errors"
 )
 
@@ -27,9 +29,11 @@ type PlanExecutor struct {
 	terraform             *TerraformClient
 	githubCommentRenderer *GithubCommentRenderer
 	lockingClient         *locking.Client
-	// LockURL is a function that given a lock id will return the url to view that lock
-	LockURL     func(id string) (url string)
-	planBackend plan.Backend
+	// LockURL is a function that given a lock id will return a url for lock view
+	LockURL      func(id string) (url string)
+	planBackend  plan.Backend
+	preRun       *prerun.PreRun
+	configReader *ConfigReader
 }
 
 /** Result Types **/
@@ -150,35 +154,55 @@ func (p *PlanExecutor) setupAndPlan(ctx *CommandContext) ExecutionResult {
 		return p.setupError(ctx, errors.Wrap(err, "cleaning workspace"))
 	}
 
-	var config Config
+	tfEnv := ctx.Command.environment
 	planOutputs := []PathResult{}
 	for _, project := range projects {
 		// check if config file is found, if not we continue the run
+		var config ProjectConfig
 		absolutePath := filepath.Join(cloneDir, project.Path)
-		if config.Exists(absolutePath) {
+		var terraformPlanExtraArgs []string
+		if p.configReader.Exists(absolutePath) {
 			ctx.Log.Info("Config file found in %s", absolutePath)
-			err := config.Read(absolutePath)
+			config, err = p.configReader.Read(absolutePath)
 			if err != nil {
 				errMsg := fmt.Sprintf("Error reading config file: %v", err)
 				ctx.Log.Err(errMsg)
 				return ExecutionResult{SetupError: GeneralError{errors.New(errMsg)}}
 			}
-			// need to use the remote state path and backend to do remote configure
-			err = PreRun(&config, ctx.Log, absolutePath, ctx.Command)
+
+			// add terraform arguments from project config
+			terraformPlanExtraArgs = config.GetExtraArguments(ctx.Command.commandType.String())
+		}
+
+		// check if terraform version is >= 0.9.0
+		terraformVersion := p.terraform.Version()
+		if config.TerraformVersion != nil {
+			terraformVersion = config.TerraformVersion
+		}
+		constraints, _ := version.NewConstraint(">= 0.9.0")
+		if constraints.Check(terraformVersion) {
+			// run terraform init and environment
+			outputs, err := p.terraform.RunTerraformInitAndEnv(absolutePath, tfEnv, config)
+			if err != nil {
+				errMsg := fmt.Sprintf("terraform init and environment commands failed. %s %v", outputs, err)
+				ctx.Log.Err(errMsg)
+				return ExecutionResult{SetupError: GeneralError{errors.New(errMsg)}}
+			}
+			ctx.Log.Info("terraform init and environment commands ran successfully %s", outputs)
+		}
+
+		// if there are pre plan commands then run them
+		if len(config.PrePlan.Commands) > 0 {
+			preRunOutput, err := p.preRun.Start(config.PrePlan.Commands, absolutePath, tfEnv, terraformVersion)
 			if err != nil {
 				errMsg := fmt.Sprintf("pre run failed: %v", err)
 				ctx.Log.Err(errMsg)
 				return ExecutionResult{SetupError: GeneralError{errors.New(errMsg)}}
 			}
-
-			// check if terraform version is specified in config
-			if config.TerraformVersion != "" {
-				p.terraform.tfExecutableName = "terraform" + config.TerraformVersion
-			} else {
-				p.terraform.tfExecutableName = "terraform"
-			}
+			ctx.Log.Info("Pre run output: \n%s", preRunOutput)
 		}
-		generatePlanResponse := p.plan(ctx, cloneDir, p.scratchDir, project, p.sshKey, config.StashPath)
+
+		generatePlanResponse := p.plan(ctx, cloneDir, p.scratchDir, project, p.sshKey, terraformPlanExtraArgs)
 		generatePlanResponse.Path = project.Path
 		planOutputs = append(planOutputs, generatePlanResponse)
 	}
@@ -194,25 +218,11 @@ func (p *PlanExecutor) plan(
 	planOutDir string,
 	project models.Project,
 	sshKey string,
-	stashPath string) PathResult {
+	terraformArgs []string) PathResult {
 	ctx.Log.Info("generating plan for path %q", project.Path)
 
-	// NOTE: THIS CODE IS TO SUPPORT TERRAFORM PROJECTS THAT AREN'T USING ATLANTIS CONFIG FILE.
-	if stashPath == "" {
-		_, err := p.terraform.ConfigureRemoteState(ctx.Log, repoDir, project, ctx.Command.environment, sshKey)
-		if err != nil {
-			return PathResult{
-				Status: Error,
-				Result: GeneralError{fmt.Errorf("failed to configure remote state: %s", err)},
-			}
-		}
-	}
-	// todo: setting environment to default should be done elsewhere
 	tfEnv := ctx.Command.environment
-	if tfEnv == "" {
-		tfEnv = "default"
-	}
-	lockAttempt, err := p.lockingClient.TryLock(project, ctx.Command.environment, ctx.Pull, ctx.User)
+	lockAttempt, err := p.lockingClient.TryLock(project, tfEnv, ctx.Pull, ctx.User)
 	if err != nil {
 		return PathResult{
 			Status: Failure,
@@ -230,21 +240,14 @@ func (p *PlanExecutor) plan(
 
 	// Run terraform plan
 	ctx.Log.Info("running terraform plan in directory %q", project.Path)
-	tfPlanCmd := []string{"plan", "-refresh", "-no-color"}
 	planFile := filepath.Join(repoDir, project.Path, fmt.Sprintf("%s.tfplan", tfEnv))
-	if ctx.Command.environment != "" {
-		tfEnvFileName := filepath.Join("env", ctx.Command.environment+".tfvars")
-		if _, err := os.Stat(filepath.Join(repoDir, project.Path, tfEnvFileName)); err == nil {
-			tfPlanCmd = append(tfPlanCmd, "-var-file", tfEnvFileName, "-out", planFile)
-		} else {
-			ctx.Log.Err("environment file %q not found", tfEnvFileName)
-			return PathResult{
-				Status: Failure,
-				Result: EnvironmentFileNotFoundFailure{tfEnvFileName},
-			}
-		}
-	} else {
-		tfPlanCmd = append(tfPlanCmd, "-out", planFile)
+	tfPlanCmd := []string{"plan", "-refresh", "-no-color", "-out", planFile}
+	// append terraform arguments from config file
+	tfPlanCmd = append(tfPlanCmd, terraformArgs...)
+	// check if env/{environment}.tfvars exist
+	tfEnvFileName := filepath.Join("env", tfEnv+".tfvars")
+	if _, err := os.Stat(filepath.Join(repoDir, project.Path, tfEnvFileName)); err == nil {
+		tfPlanCmd = append(tfPlanCmd, "-var-file", tfEnvFileName)
 	}
 
 	// set pull request creator as the session name
@@ -386,11 +389,6 @@ func (p *PlanExecutor) CleanWorkspace(log *logging.SimpleLogger, deleteFilesPref
 	return nil
 }
 
-// todo: make OO
-func generateStatePath(path string, tfEnvName string) string {
-	return strings.Replace(path, "$ENVIRONMENT", tfEnvName, -1)
-}
-
 func (p *PlanExecutor) setupError(ctx *CommandContext, err error) ExecutionResult {
 	ctx.Log.Err(err.Error())
 	p.githubStatus.Update(ctx.Repo, ctx.Pull, Error, PlanStep)
diff --git a/server/pre_run.go b/server/pre_run.go
deleted file mode 100644
index e8a52efdd..000000000
--- a/server/pre_run.go
+++ /dev/null
@@ -1,100 +0,0 @@
-package server
-
-import (
-	"bufio"
-	"fmt"
-	"github.com/hootsuite/atlantis/logging"
-	"io/ioutil"
-	"os"
-	"os/exec"
-)
-
-const InlineShebang = "/bin/sh -e"
-
-// todo: make OO
-// PreRun is a function that will determine whether
-func PreRun(c *Config, log *logging.SimpleLogger, path string, command *Command) error {
-	log.Info("Staring pre run in %s", path)
-	var execScript string
-
-	if command.commandType == Plan {
-		// we create a script from the commands provided
-		s, err := createScript(c.PrePlan.Commands)
-		if err != nil {
-			return err
-		}
-		execScript = s
-	}
-	if command.commandType == Apply {
-		// we create a script from the commands provided
-		s, err := createScript(c.PreApply.Commands)
-		if err != nil {
-			return err
-		}
-		execScript = s
-	}
-
-	if execScript != "" {
-		defer os.Remove(execScript)
-		log.Info("Running script %s", execScript)
-		// set environment variable for the run.
-		// this is to support scripts to use the ENVIRONMENT and WORKSPACE variables in their scripts
-		if command.environment != "" {
-			os.Setenv("ENVIRONMENT", command.environment)
-		}
-		if c.TerraformVersion != "" {
-			os.Setenv("ATLANTIS_TERRAFORM_VERSION", c.TerraformVersion)
-		}
-		os.Setenv("WORKSPACE", path)
-		output, err := execute(execScript)
-		if err != nil {
-			return err
-		}
-		log.Info("output: \n%s", output)
-	}
-
-	return nil
-
-}
-
-func createScript(cmds []string) (string, error) {
-	var scriptName string
-	if cmds != nil {
-		tmp, err := ioutil.TempFile("/tmp", "atlantis-temp-script")
-		if err != nil {
-			return "", fmt.Errorf("Error preparing shell script: %s", err)
-		}
-
-		scriptName = tmp.Name()
-
-		// Write our contents to it
-		writer := bufio.NewWriter(tmp)
-		writer.WriteString(fmt.Sprintf("#!%s\n", InlineShebang))
-		for _, command := range cmds {
-			if _, err := writer.WriteString(command + "\n"); err != nil {
-				return "", fmt.Errorf("Error preparing script: %s", err)
-			}
-		}
-
-		if err := writer.Flush(); err != nil {
-			return "", fmt.Errorf("Error flushing file when preparing script: %s", err)
-		}
-		tmp.Close()
-	}
-
-	return scriptName, nil
-}
-
-func execute(script string) (string, error) {
-	if _, err := os.Stat(script); err == nil {
-		os.Chmod(script, 0775)
-	}
-	localCmd := exec.Command("sh", "-c", script)
-	out, err := localCmd.CombinedOutput()
-	output := string(out)
-	if err != nil {
-		return output, fmt.Errorf("Error running script %s: %v %s", script, err, output)
-	}
-
-	return output, nil
-}
diff --git a/server/project_config.go b/server/project_config.go
new file mode 100644
index 000000000..6b9110ec4
--- /dev/null
+++ b/server/project_config.go
@@ -0,0 +1,88 @@
+package server
+
+import (
+	"fmt"
+	"io/ioutil"
+	"os"
+	"path/filepath"
+
+	version "github.com/hashicorp/go-version"
+	"github.com/pkg/errors"
+
+	yaml "gopkg.in/yaml.v2"
+)
+
+const ProjectConfigFile = "atlantis.yaml"
+
+type PrePlan struct {
+	Commands []string `yaml:"commands"`
+}
+
+type PreApply struct {
+	Commands []string `yaml:"commands"`
+}
+
+type ConfigReader struct{}
+
+type ProjectConfigYaml struct {
+	PrePlan          PrePlan                 `yaml:"pre_plan"`
+	PreApply         PreApply                `yaml:"pre_apply"`
+	TerraformVersion string                  `yaml:"terraform_version"`
+	ExtraArguments   []CommandExtraArguments `yaml:"extra_arguments"`
+}
+
+type ProjectConfig struct {
+	PrePlan  PrePlan
+	PreApply PreApply
+	// TerraformVersion is the version specified in the config file or nil if version wasn't specified
+	TerraformVersion *version.Version
+	ExtraArguments   []CommandExtraArguments
+}
+
+type CommandExtraArguments struct {
+	Name      string   `yaml:"command_name"`
+	Arguments []string `yaml:"arguments"`
+}
+
+func (c *ConfigReader) Exists(execPath string) bool {
+	// Check if config file exists
+	_, err := os.Stat(filepath.Join(execPath, ProjectConfigFile))
+	return err == nil
+}
+
+func (c *ConfigReader) Read(execPath string) (ProjectConfig, error) {
+	var pc ProjectConfig
+	raw, err := ioutil.ReadFile(filepath.Join(execPath, ProjectConfigFile))
+	if err != nil {
+		return pc, fmt.Errorf("Couldn't read config file %q: %v", execPath, err)
+	}
+	var pcYaml ProjectConfigYaml
+	if err := yaml.Unmarshal(raw, &pcYaml); err != nil {
+		return pc, fmt.Errorf("Couldn't decode yaml in config file %q: %v", execPath, err)
+	}
+
+	var v *version.Version
+	if pcYaml.TerraformVersion != "" {
+		v, err = version.NewVersion(pcYaml.TerraformVersion)
+		if err != nil {
+			return pc, errors.Wrap(err, "parsing terraform_version")
+		}
+	}
+	pc = ProjectConfig{
+		TerraformVersion: v,
+		ExtraArguments:   pcYaml.ExtraArguments,
+		PreApply:         pcYaml.PreApply,
+		PrePlan:          pcYaml.PrePlan,
+	}
+
+	return pc, nil
+}
+
+func (c *ProjectConfig) GetExtraArguments(command string) []string {
+	for _, value := range c.ExtraArguments {
+		if value.Name == command {
+			return value.Arguments
+		}
+	}
+	return nil
+}
diff --git a/server/atlantis_config_file_test.go b/server/project_config_test.go
similarity index 63%
rename from server/atlantis_config_file_test.go
rename to server/project_config_test.go
index efc98e58b..6573724fd 100644
--- a/server/atlantis_config_file_test.go
+++ b/server/project_config_test.go
@@ -1,22 +1,15 @@
 package server
 
 import (
-	. "github.com/hootsuite/atlantis/testing_util"
 	"io/ioutil"
 	"os"
 	"testing"
+
+	. "github.com/hootsuite/atlantis/testing_util"
 )
 
-var tempConfigFile = "/tmp/" + AtlantisConfigFile
-
-func TestConfigFileExists_invalid_path(t *testing.T) {
-	var c Config
-	Equals(t, c.Exists("/invalid/path"), false)
-}
-
-func TestConfigFileExists_valid_path(t *testing.T) {
-	var c Config
-	var str = `
+var tempConfigFile = "/tmp/" + ProjectConfigFile
+var projectConfigFileStr = `
 ---
 terraform_version: "0.0.1"
 pre_apply:
@@ -27,41 +20,38 @@ pre_plan:
   commands:
     - "echo"
     - "date"
-stash_path: "file/path"
+extra_arguments:
+  - command_name: "plan"
+    arguments: ["-var", "hello=world"]
 `
-	writeAtlantisConfigFile([]byte(str))
+
+func TestConfigFileExists_invalid_path(t *testing.T) {
+	var c ConfigReader
+	Equals(t, c.Exists("/invalid/path"), false)
+}
+
+func TestConfigFileExists_valid_path(t *testing.T) {
+	var c ConfigReader
+	writeAtlantisConfigFile([]byte(projectConfigFileStr))
 	defer os.Remove(tempConfigFile)
 	Equals(t, c.Exists("/tmp"), true)
 }
 
 func TestConfigFileRead_invalid_config(t *testing.T) {
-	var c Config
+	var c ConfigReader
 	str := []byte(`---invalid`)
 	writeAtlantisConfigFile(str)
 	defer os.Remove(tempConfigFile)
-	err := c.Read("/tmp")
+	_, err := c.Read("/tmp")
 	Assert(t, err != nil, "expect an error")
 }
 
 func TestConfigFileRead_valid_config(t *testing.T) {
-	var c Config
-	var str = `
----
-terraform_version: "0.0.1"
-pre_apply:
-  commands:
-    - "echo"
-    - "date"
-pre_plan:
-  commands:
-    - "echo"
-    - "date"
-stash_path: "file/path"
-`
-	writeAtlantisConfigFile([]byte(str))
+	var c ConfigReader
+	writeAtlantisConfigFile([]byte(projectConfigFileStr))
 	defer os.Remove(tempConfigFile)
-	err := c.Read("/tmp")
-	Assert(t, err == nil, "should be valid json")
+	_, err := c.Read("/tmp")
+	Assert(t, err == nil, "should be valid yaml")
 }
 
 func writeAtlantisConfigFile(s []byte) error {
diff --git a/server/server.go b/server/server.go
index 032fd5635..5e1797109 100644
--- a/server/server.go
+++ b/server/server.go
@@ -29,6 +29,7 @@ import (
 	"github.com/pkg/errors"
 	"github.com/urfave/cli"
 	"github.com/urfave/negroni"
+	"github.com/hootsuite/atlantis/prerun"
 )
 
 const (
@@ -41,14 +42,14 @@ const (
 
 // Server listens for GitHub events and runs the necessary Atlantis command
 type Server struct {
-	router         *mux.Router
-	port           int
-	commandHandler *CommandHandler
+	router             *mux.Router
+	port               int
+	commandHandler     *CommandHandler
 	pullClosedExecutor *PullClosedExecutor
-	logger         *logging.SimpleLogger
-	eventParser    *EventParser
-	lockingClient  *locking.Client
-	atlantisURL    string
+	logger             *logging.SimpleLogger
+	eventParser        *EventParser
+	lockingClient      *locking.Client
+	atlantisURL        string
 }
 
 // the mapstructure tags correspond to flags in cmd/server.go
@@ -108,6 +109,7 @@ func (g GeneralError) Template() *CompiledTemplate {
 
 // todo: /end
 
+
 func NewServer(config ServerConfig) (*Server, error) {
 	tp := github.BasicAuthTransport{
 		Username: strings.TrimSpace(config.GithubUser),
@@ -122,8 +124,9 @@ func NewServer(config ServerConfig) (*Server, error) {
 	githubBaseClient.BaseURL, _ = url.Parse(ghHostname)
 	githubClient := &GithubClient{client: githubBaseClient, ctx: githubClientCtx}
 	githubStatus := &GithubStatus{client: githubClient}
-	terraformClient := &TerraformClient{
-		tfExecutableName: "terraform",
+	terraformClient, err := NewTerraformClient()
+	if err != nil {
+		return nil, errors.Wrap(err, "initializing terraform")
 	}
 	githubComments := &GithubCommentRenderer{}
 	awsConfig := &AWSConfig{
@@ -133,7 +136,6 @@ func NewServer(config ServerConfig) (*Server, error) {
 
 	var awsSession *session.Session
 	var lockingClient *locking.Client
-	var err error
 	if config.LockingBackend == LockingDynamoDBBackend {
 		awsSession, err = awsConfig.CreateAWSSession()
 		if err != nil {
@@ -162,6 +164,8 @@ func NewServer(config ServerConfig) (*Server, error) {
 			return nil, errors.Wrap(err, "creating file backend for plans")
 		}
 	}
+	preRun := &prerun.PreRun{}
+	configReader := &ConfigReader{}
 	applyExecutor := &ApplyExecutor{
 		github:                githubClient,
 		githubStatus:          githubStatus,
@@ -173,6 +177,8 @@ func NewServer(config ServerConfig) (*Server, error) {
 		lockingClient:         lockingClient,
 		requireApproval:       config.RequireApproval,
 		planBackend:           planBackend,
+		preRun:                preRun,
+		configReader: configReader,
 	}
 	planExecutor := &PlanExecutor{
 		github:                githubClient,
@@ -184,12 +190,14 @@ func NewServer(config ServerConfig) (*Server, error) {
 		githubCommentRenderer: githubComments,
 		lockingClient:         lockingClient,
 		planBackend:           planBackend,
+		preRun:                preRun,
+		configReader: configReader,
 	}
 	helpExecutor := &HelpExecutor{}
 	pullClosedExecutor := &PullClosedExecutor{
 		planBackend: planBackend,
-		github: githubClient,
-		locking: lockingClient,
+		github:      githubClient,
+		locking:     lockingClient,
 	}
 	logger := logging.NewSimpleLogger("server", log.New(os.Stderr, "", log.LstdFlags), false, logging.ToLogLevel(config.LogLevel))
 	eventParser := &EventParser{}
@@ -203,14 +211,14 @@ func NewServer(config ServerConfig) (*Server, error) {
 	}
 	router := mux.NewRouter()
 	return &Server{
-		router:         router,
-		port:           config.Port,
-		commandHandler: commandHandler,
+		router:             router,
+		port:               config.Port,
+		commandHandler:     commandHandler,
 		pullClosedExecutor: pullClosedExecutor,
-		eventParser:    eventParser,
-		logger:         logger,
-		lockingClient:  lockingClient,
-		atlantisURL:    config.AtlantisURL,
+		eventParser:        eventParser,
+		logger:             logger,
+		lockingClient:      lockingClient,
+		atlantisURL:        config.AtlantisURL,
 	}, nil
 }
 
diff --git a/server/terraform_client.go b/server/terraform_client.go
index 42cf3c057..863a78362 100644
--- a/server/terraform_client.go
+++ b/server/terraform_client.go
@@ -2,82 +2,63 @@ package server
 
 import (
 	"fmt"
-	"github.com/hootsuite/atlantis/logging"
-	"github.com/hootsuite/atlantis/models"
-	"os"
 	"os/exec"
-	"path/filepath"
 	"regexp"
+
+	version "github.com/hashicorp/go-version"
+	"github.com/pkg/errors"
 )
 
 type TerraformClient struct {
-	tfExecutableName string
+	defaultVersion *version.Version
 }
 
-func (t *TerraformClient) ConfigureRemoteState(log *logging.SimpleLogger, repoDir string, project models.Project, env string, sshKey string) (string, error) {
-	absolutePath := filepath.Join(repoDir, project.Path)
-	log.Info("setting up remote state in directory %q", absolutePath)
-	var remoteSetupCmdArgs []string
+var terraformVersionRegex = regexp.MustCompile("Terraform v(.*)\n")
 
-	// Check if setup file exists
-	setupFileInfo, err := os.Stat(filepath.Join(absolutePath, "setup.sh"))
+func NewTerraformClient() (*TerraformClient, error) {
+	versionCmdOutput, err := exec.Command("terraform", "version").CombinedOutput()
+	output := string(versionCmdOutput)
 	if err != nil {
-		return "", fmt.Errorf("setup.sh file doesn't exist in terraform plan path %q: %v", project.Path, err)
-	}
-	// Check if setup file is executed
-	if setupFileInfo.Mode() != os.FileMode(0755) {
-		return "", fmt.Errorf("setup file isn't executable, required permissions are 0755")
-	}
-	// Check if environment is specified
-	if env == "" {
-		// Check if env/ folder exist and environment isn't specified
-		// todo: make env a constant (environmentDirName)
-		if _, err := os.Stat(filepath.Join(absolutePath, "env")); err == nil {
-			log.Info("environment directory exists but no environment was supplied")
-			return "", nil
-		}
-	} else {
-		// Check if the environment file exists
-		envFile := env + ".tfvars"
-		envPath := filepath.Join(absolutePath, "env")
-		if _, err := os.Stat(filepath.Join(envPath, envFile)); err != nil {
-			return "", fmt.Errorf("environment file %q not found in %q", envFile, envPath)
+		// exec.go line 35, Error() returns
+		// "exec: " + strconv.Quote(e.Name) + ": " + e.Err.Error()
+		if err.Error() == fmt.Sprintf("exec: \"terraform\": %s", exec.ErrNotFound.Error()) {
+			return nil, errors.New("terraform not found in $PATH. \n\nDownload terraform from https://www.terraform.io/downloads.html")
 		}
+		return nil, errors.Wrapf(err, "running terraform version: %s", output)
 	}
-
-	// Set environment file parameter for ./setup.sh
-	if env != "" {
-		remoteSetupCmdArgs = append(remoteSetupCmdArgs, "-e", env)
+	match := terraformVersionRegex.FindStringSubmatch(output)
+	if len(match) <= 1 {
+		return nil, fmt.Errorf("could not parse terraform version from %s", output)
 	}
-	remoteSetupCmd := exec.Command("./setup.sh", remoteSetupCmdArgs...)
-	remoteSetupCmd.Dir = absolutePath
-	// Check if ssh key is set
-	if sshKey != "" {
-		// Fixing a bug when git isn't found in path when environment variables are set for command
-		remoteSetupCmd.Env = os.Environ()
-		remoteSetupCmd.Env = append(remoteSetupCmd.Env, fmt.Sprintf("GIT_SSH=%s", defaultSSHWrapper), fmt.Sprintf("PKEY=%s", sshKey))
-
-	}
-	out, err := remoteSetupCmd.CombinedOutput()
-	output := string(out[:])
-	log.Info("setup.sh output: \n%s", output)
+	version, err := version.NewVersion(match[1])
 	if err != nil {
-		return "", fmt.Errorf("failed to configure remote state: %v", err)
+		return nil, errors.Wrap(err, "parsing terraform version")
 	}
-	// Get remote state path from setup.sh output
-	r, _ := regexp.Compile("REMOTE_STATE_PATH=([^ ]*.tfstate)")
-	match := r.FindStringSubmatch(output)
-	// Backend remote state path
-	remoteStatePath := match[1]
-	log.Info("remote state path %q", remoteStatePath)
 
-	return remoteStatePath, nil
+	return &TerraformClient{
+		defaultVersion: version,
+	}, nil
 }
 
-func (t *TerraformClient) RunTerraformCommand(path string, tfPlanCmd []string, tfEnvVars []string) ([]string, string, error) {
-	terraformCmd := exec.Command(t.tfExecutableName, tfPlanCmd...)
+func (t *TerraformClient) RunTerraformCommand(path string, tfCmd []string, tfEnvVars []string) ([]string, string, error) {
+	return t.RunTerraformCommandWithVersion(path, tfCmd, tfEnvVars, t.defaultVersion)
+}
+
+func (t *TerraformClient) Version() *version.Version {
+	return t.defaultVersion
+}
+
+func (t *TerraformClient) RunTerraformCommandWithVersion(path string, tfCmd []string, tfEnvVars []string, v *version.Version) ([]string, string, error) {
+	tfExecutable := "terraform"
+	// if version is the same as the default, don't need to prepend the version name to the executable
+	if !v.Equal(t.defaultVersion) {
+		tfExecutable = fmt.Sprintf("%s%s", tfExecutable, v.String())
+	}
+	terraformCmd := exec.Command(tfExecutable, tfCmd...)
 	terraformCmd.Dir = path
-	terraformCmd.Env = tfEnvVars
+	if len(tfEnvVars) > 0 {
+		terraformCmd.Env = tfEnvVars
+	}
 	out, err := terraformCmd.CombinedOutput()
 	output := string(out)
 	if err != nil {
@@ -86,3 +67,25 @@ func (t *TerraformClient) RunTerraformCommand(path string, tfPlanCmd []string, t
 
 	return terraformCmd.Args, output, nil
 }
+
+func (t *TerraformClient) RunTerraformInitAndEnv(path string, env string, config ProjectConfig) ([]string, error) {
+	var outputs []string
+	// run terraform init
+	_, output, err := t.RunTerraformCommand(path, append([]string{"init", "-no-color"}, config.GetExtraArguments("init")...), []string{})
+	if err != nil {
+		return nil, errors.Wrapf(err, "running terraform init: %s", output)
+	}
+	outputs = append(outputs, output)
+
+	// run terraform env new and select
+	_, output, err = t.RunTerraformCommand(path, []string{"env", "select", "-no-color", env}, []string{})
+	if err != nil {
+		// if terraform env select fails we will run terraform env new
+		// to create a new environment
+		_, output, err = t.RunTerraformCommand(path, []string{"env", "new", "-no-color", env}, []string{})
+		if err != nil {
+			return nil, errors.Wrapf(err, "running terraform environment command: %s", output)
+		}
+	}
+	return append(outputs, output), nil
+}
diff --git a/vendor/github.com/hashicorp/go-version/LICENSE b/vendor/github.com/hashicorp/go-version/LICENSE
new file mode 100644
index 000000000..c33dcc7c9
--- /dev/null
+++ b/vendor/github.com/hashicorp/go-version/LICENSE
@@ -0,0 +1,354 @@
+Mozilla Public License, version 2.0
+
+1. Definitions
+
+1.1. “Contributor”
+
+     means each individual or legal entity that creates, contributes to the
+     creation of, or owns Covered Software.
+
+1.2. “Contributor Version”
+
+     means the combination of the Contributions of others (if any) used by a
+     Contributor and that particular Contributor’s Contribution.
+
+1.3. “Contribution”
+
+     means Covered Software of a particular Contributor.
+
+1.4. “Covered Software”
+
+     means Source Code Form to which the initial Contributor has attached the
+     notice in Exhibit A, the Executable Form of such Source Code Form, and
+     Modifications of such Source Code Form, in each case including portions
+     thereof.
+
+1.5. “Incompatible With Secondary Licenses”
+     means
+
+     a. that the initial Contributor has attached the notice described in
+        Exhibit B to the Covered Software; or
+
+     b. that the Covered Software was made available under the terms of version
+        1.1 or earlier of the License, but not also under the terms of a
+        Secondary License.
+
+1.6. “Executable Form”
+
+     means any form of the work other than Source Code Form.
+
+1.7. “Larger Work”
+
+     means a work that combines Covered Software with other material, in a separate
+     file or files, that is not Covered Software.
+
+1.8. “License”
+
+     means this document.
+
+1.9. “Licensable”
+
+     means having the right to grant, to the maximum extent possible, whether at the
+     time of the initial grant or subsequently, any and all of the rights conveyed by
+     this License.
+
+1.10. “Modifications”
+
+     means any of the following:
+
+     a. any file in Source Code Form that results from an addition to, deletion
+        from, or modification of the contents of Covered Software; or
+
+     b. any new file in Source Code Form that contains any Covered Software.
+
+1.11. “Patent Claims” of a Contributor
+
+      means any patent claim(s), including without limitation, method, process,
+      and apparatus claims, in any patent Licensable by such Contributor that
+      would be infringed, but for the grant of the License, by the making,
+      using, selling, offering for sale, having made, import, or transfer of
+      either its Contributions or its Contributor Version.
+
+1.12. “Secondary License”
+
+      means either the GNU General Public License, Version 2.0, the GNU Lesser
+      General Public License, Version 2.1, the GNU Affero General Public
+      License, Version 3.0, or any later versions of those licenses.
+
+1.13. “Source Code Form”
+
+      means the form of the work preferred for making modifications.
+
+1.14. “You” (or “Your”)
+
+      means an individual or a legal entity exercising rights under this
+      License. For legal entities, “You” includes any entity that controls, is
+      controlled by, or is under common control with You. For purposes of this
+      definition, “control” means (a) the power, direct or indirect, to cause
+      the direction or management of such entity, whether by contract or
+      otherwise, or (b) ownership of more than fifty percent (50%) of the
+      outstanding shares or beneficial ownership of such entity.
+
+
+2. License Grants and Conditions
+
+2.1. Grants
+
+     Each Contributor hereby grants You a world-wide, royalty-free,
+     non-exclusive license:
+
+     a. under intellectual property rights (other than patent or trademark)
+        Licensable by such Contributor to use, reproduce, make available,
+        modify, display, perform, distribute, and otherwise exploit its
+        Contributions, either on an unmodified basis, with Modifications, or as
+        part of a Larger Work; and
+
+     b. under Patent Claims of such Contributor to make, use, sell, offer for
+        sale, have made, import, and otherwise transfer either its Contributions
+        or its Contributor Version.
+
+2.2. Effective Date
+
+     The licenses granted in Section 2.1 with respect to any Contribution become
+     effective for each Contribution on the date the Contributor first distributes
+     such Contribution.
+
+2.3. Limitations on Grant Scope
+
+     The licenses granted in this Section 2 are the only rights granted under this
+     License. No additional rights or licenses will be implied from the distribution
+     or licensing of Covered Software under this License. Notwithstanding Section
+     2.1(b) above, no patent license is granted by a Contributor:
+
+     a. for any code that a Contributor has removed from Covered Software; or
+
+     b. for infringements caused by: (i) Your and any other third party’s
+        modifications of Covered Software, or (ii) the combination of its
+        Contributions with other software (except as part of its Contributor
+        Version); or
+
+     c. under Patent Claims infringed by Covered Software in the absence of its
+        Contributions.
+
+     This License does not grant any rights in the trademarks, service marks, or
+     logos of any Contributor (except as may be necessary to comply with the
+     notice requirements in Section 3.4).
+
+2.4. Subsequent Licenses
+
+     No Contributor makes additional grants as a result of Your choice to
+     distribute the Covered Software under a subsequent version of this License
+     (see Section 10.2) or under the terms of a Secondary License (if permitted
+     under the terms of Section 3.3).
+
+2.5. Representation
+
+     Each Contributor represents that the Contributor believes its Contributions
+     are its original creation(s) or it has sufficient rights to grant the
+     rights to its Contributions conveyed by this License.
+
+2.6. Fair Use
+
+     This License is not intended to limit any rights You have under applicable
+     copyright doctrines of fair use, fair dealing, or other equivalents.
+
+2.7. Conditions
+
+     Sections 3.1, 3.2, 3.3, and 3.4 are conditions of the licenses granted in
+     Section 2.1.
+
+
+3. Responsibilities
+
+3.1. Distribution of Source Form
+
+     All distribution of Covered Software in Source Code Form, including any
+     Modifications that You create or to which You contribute, must be under the
+     terms of this License. You must inform recipients that the Source Code Form
+     of the Covered Software is governed by the terms of this License, and how
+     they can obtain a copy of this License. You may not attempt to alter or
+     restrict the recipients’ rights in the Source Code Form.
+
+3.2. Distribution of Executable Form
+
+     If You distribute Covered Software in Executable Form then:
+
+     a. such Covered Software must also be made available in Source Code Form,
+        as described in Section 3.1, and You must inform recipients of the
+        Executable Form how they can obtain a copy of such Source Code Form by
+        reasonable means in a timely manner, at a charge no more than the cost
+        of distribution to the recipient; and
+
+     b. You may distribute such Executable Form under the terms of this License,
+        or sublicense it under different terms, provided that the license for
+        the Executable Form does not attempt to limit or alter the recipients’
+        rights in the Source Code Form under this License.
+
+3.3. Distribution of a Larger Work
+
+     You may create and distribute a Larger Work under terms of Your choice,
+     provided that You also comply with the requirements of this License for the
+     Covered Software. If the Larger Work is a combination of Covered Software
+     with a work governed by one or more Secondary Licenses, and the Covered
+     Software is not Incompatible With Secondary Licenses, this License permits
+     You to additionally distribute such Covered Software under the terms of
+     such Secondary License(s), so that the recipient of the Larger Work may, at
+     their option, further distribute the Covered Software under the terms of
+     either this License or such Secondary License(s).
+
+3.4. Notices
+
+     You may not remove or alter the substance of any license notices (including
+     copyright notices, patent notices, disclaimers of warranty, or limitations
+     of liability) contained within the Source Code Form of the Covered
+     Software, except that You may alter any license notices to the extent
+     required to remedy known factual inaccuracies.
+
+3.5. Application of Additional Terms
+
+     You may choose to offer, and to charge a fee for, warranty, support,
+     indemnity or liability obligations to one or more recipients of Covered
+     Software. However, You may do so only on Your own behalf, and not on behalf
+     of any Contributor. You must make it absolutely clear that any such
+     warranty, support, indemnity, or liability obligation is offered by You
+     alone, and You hereby agree to indemnify every Contributor for any
+     liability incurred by such Contributor as a result of warranty, support,
+     indemnity or liability terms You offer. You may include additional
+     disclaimers of warranty and limitations of liability specific to any
+     jurisdiction.
+
+4. Inability to Comply Due to Statute or Regulation
+
+   If it is impossible for You to comply with any of the terms of this License
+   with respect to some or all of the Covered Software due to statute, judicial
+   order, or regulation then You must: (a) comply with the terms of this License
+   to the maximum extent possible; and (b) describe the limitations and the code
+   they affect. Such description must be placed in a text file included with all
+   distributions of the Covered Software under this License. Except to the
+   extent prohibited by statute or regulation, such description must be
+   sufficiently detailed for a recipient of ordinary skill to be able to
+   understand it.
+
+5. Termination
+
+5.1. The rights granted under this License will terminate automatically if You
+     fail to comply with any of its terms. However, if You become compliant,
+     then the rights granted under this License from a particular Contributor
+     are reinstated (a) provisionally, unless and until such Contributor
+     explicitly and finally terminates Your grants, and (b) on an ongoing basis,
+     if such Contributor fails to notify You of the non-compliance by some
+     reasonable means prior to 60 days after You have come back into compliance.
+     Moreover, Your grants from a particular Contributor are reinstated on an
+     ongoing basis if such Contributor notifies You of the non-compliance by
+     some reasonable means, this is the first time You have received notice of
+     non-compliance with this License from such Contributor, and You become
+     compliant prior to 30 days after Your receipt of the notice.
+
+5.2. If You initiate litigation against any entity by asserting a patent
+     infringement claim (excluding declaratory judgment actions, counter-claims,
+     and cross-claims) alleging that a Contributor Version directly or
+     indirectly infringes any patent, then the rights granted to You by any and
+     all Contributors for the Covered Software under Section 2.1 of this License
+     shall terminate.
+
+5.3. In the event of termination under Sections 5.1 or 5.2 above, all end user
+     license agreements (excluding distributors and resellers) which have been
+     validly granted by You or Your distributors under this License prior to
+     termination shall survive termination.
+
+6. Disclaimer of Warranty
+
+   Covered Software is provided under this License on an “as is” basis, without
+   warranty of any kind, either expressed, implied, or statutory, including,
+   without limitation, warranties that the Covered Software is free of defects,
+   merchantable, fit for a particular purpose or non-infringing. The entire
+   risk as to the quality and performance of the Covered Software is with You.
+   Should any Covered Software prove defective in any respect, You (not any
+   Contributor) assume the cost of any necessary servicing, repair, or
+   correction. This disclaimer of warranty constitutes an essential part of this
+   License. No use of  any Covered Software is authorized under this License
+   except under this disclaimer.
+
+7. Limitation of Liability
+
+   Under no circumstances and under no legal theory, whether tort (including
+   negligence), contract, or otherwise, shall any Contributor, or anyone who
+   distributes Covered Software as permitted above, be liable to You for any
+   direct, indirect, special, incidental, or consequential damages of any
+   character including, without limitation, damages for lost profits, loss of
+   goodwill, work stoppage, computer failure or malfunction, or any and all
+   other commercial damages or losses, even if such party shall have been
+   informed of the possibility of such damages. This limitation of liability
+   shall not apply to liability for death or personal injury resulting from such
+   party’s negligence to the extent applicable law prohibits such limitation.
+   Some jurisdictions do not allow the exclusion or limitation of incidental or
+   consequential damages, so this exclusion and limitation may not apply to You.
+
+8. Litigation
+
+   Any litigation relating to this License may be brought only in the courts of
+   a jurisdiction where the defendant maintains its principal place of business
+   and such litigation shall be governed by laws of that jurisdiction, without
+   reference to its conflict-of-law provisions. Nothing in this Section shall
+   prevent a party’s ability to bring cross-claims or counter-claims.
+
+9. Miscellaneous
+
+   This License represents the complete agreement concerning the subject matter
+   hereof. If any provision of this License is held to be unenforceable, such
+   provision shall be reformed only to the extent necessary to make it
+   enforceable. Any law or regulation which provides that the language of a
+   contract shall be construed against the drafter shall not be used to construe
+   this License against a Contributor.
+
+
+10. Versions of the License
+
+10.1. New Versions
+
+      Mozilla Foundation is the license steward. Except as provided in Section
+      10.3, no one other than the license steward has the right to modify or
+      publish new versions of this License. Each version will be given a
+      distinguishing version number.
+
+10.2. Effect of New Versions
+
+      You may distribute the Covered Software under the terms of the version of
+      the License under which You originally received the Covered Software, or
+      under the terms of any subsequent version published by the license
+      steward.
+
+10.3. Modified Versions
+
+      If you create software not governed by this License, and you want to
+      create a new license for such software, you may create and use a modified
+      version of this License if you rename the license and remove any
+      references to the name of the license steward (except to note that such
+      modified license differs from this License).
+
+10.4. Distributing Source Code Form that is Incompatible With Secondary Licenses
+      If You choose to distribute Source Code Form that is Incompatible With
+      Secondary Licenses under the terms of this version of the License, the
+      notice described in Exhibit B of this License must be attached.
+
+Exhibit A - Source Code Form License Notice
+
+      This Source Code Form is subject to the
+      terms of the Mozilla Public License, v.
+      2.0. If a copy of the MPL was not
+      distributed with this file, You can
+      obtain one at
+      http://mozilla.org/MPL/2.0/.
+
+If it is not possible or desirable to put the notice in a particular file, then
+You may include the notice in a location (such as a LICENSE file in a relevant
+directory) where a recipient would be likely to look for such a notice.
+
+You may add additional accurate notices of copyright ownership.
+
+Exhibit B - “Incompatible With Secondary Licenses” Notice
+
+      This Source Code Form is “Incompatible
+      With Secondary Licenses”, as defined by
+      the Mozilla Public License, v. 2.0.
+
diff --git a/vendor/github.com/hashicorp/go-version/README.md b/vendor/github.com/hashicorp/go-version/README.md
new file mode 100644
index 000000000..6f3a15ce7
--- /dev/null
+++ b/vendor/github.com/hashicorp/go-version/README.md
@@ -0,0 +1,65 @@
+# Versioning Library for Go
+[![Build Status](https://travis-ci.org/hashicorp/go-version.svg?branch=master)](https://travis-ci.org/hashicorp/go-version)
+
+go-version is a library for parsing versions and version constraints,
+and verifying versions against a set of constraints. go-version
+can sort a collection of versions properly, handles prerelease/beta
+versions, can increment versions, etc.
+
+Versions used with go-version must follow [SemVer](http://semver.org/).
+
+## Installation and Usage
+
+Package documentation can be found on
+[GoDoc](http://godoc.org/github.com/hashicorp/go-version).
+
+Installation can be done with a normal `go get`:
+
+```
+$ go get github.com/hashicorp/go-version
+```
+
+#### Version Parsing and Comparison
+
+```go
+v1, err := version.NewVersion("1.2")
+v2, err := version.NewVersion("1.5+metadata")
+
+// Comparison example. There is also GreaterThan, Equal, and just
+// a simple Compare that returns an int allowing easy >=, <=, etc.
+if v1.LessThan(v2) {
+    fmt.Printf("%s is less than %s", v1, v2)
+}
+```
+
+#### Version Constraints
+
+```go
+v1, err := version.NewVersion("1.2")
+
+// Constraints example.
+constraints, err := version.NewConstraint(">= 1.0, < 1.4")
+if constraints.Check(v1) {
+	fmt.Printf("%s satisfies constraints %s", v1, constraints)
+}
+```
+
+#### Version Sorting
+
+```go
+versionsRaw := []string{"1.1", "0.7.1", "1.4-beta", "1.4", "2"}
+versions := make([]*version.Version, len(versionsRaw))
+for i, raw := range versionsRaw {
+    v, _ := version.NewVersion(raw)
+    versions[i] = v
+}
+
+// After this, the versions are properly sorted
+sort.Sort(version.Collection(versions))
+```
+
+## Issues and Contributing
+
+If you find an issue with this library, please report an issue. If you'd
+like, we welcome any contributions. Fork this library and submit a pull
+request.
diff --git a/vendor/github.com/hashicorp/go-version/constraint.go b/vendor/github.com/hashicorp/go-version/constraint.go
new file mode 100644
index 000000000..8c73df060
--- /dev/null
+++ b/vendor/github.com/hashicorp/go-version/constraint.go
@@ -0,0 +1,178 @@
+package version
+
+import (
+	"fmt"
+	"regexp"
+	"strings"
+)
+
+// Constraint represents a single constraint for a version, such as
+// ">= 1.0".
+type Constraint struct {
+	f        constraintFunc
+	check    *Version
+	original string
+}
+
+// Constraints is a slice of constraints. We make a custom type so that
+// we can add methods to it.
+type Constraints []*Constraint
+
+type constraintFunc func(v, c *Version) bool
+
+var constraintOperators map[string]constraintFunc
+
+var constraintRegexp *regexp.Regexp
+
+func init() {
+	constraintOperators = map[string]constraintFunc{
+		"":   constraintEqual,
+		"=":  constraintEqual,
+		"!=": constraintNotEqual,
+		">":  constraintGreaterThan,
+		"<":  constraintLessThan,
+		">=": constraintGreaterThanEqual,
+		"<=": constraintLessThanEqual,
+		"~>": constraintPessimistic,
+	}
+
+	ops := make([]string, 0, len(constraintOperators))
+	for k := range constraintOperators {
+		ops = append(ops, regexp.QuoteMeta(k))
+	}
+
+	constraintRegexp = regexp.MustCompile(fmt.Sprintf(
+		`^\s*(%s)\s*(%s)\s*$`,
+		strings.Join(ops, "|"),
+		VersionRegexpRaw))
+}
+
+// NewConstraint will parse one or more constraints from the given
+// constraint string. The string must be a comma-separated list of
+// constraints.
+func NewConstraint(v string) (Constraints, error) {
+	vs := strings.Split(v, ",")
+	result := make([]*Constraint, len(vs))
+	for i, single := range vs {
+		c, err := parseSingle(single)
+		if err != nil {
+			return nil, err
+		}
+
+		result[i] = c
+	}
+
+	return Constraints(result), nil
+}
+
+// Check tests if a version satisfies all the constraints.
+func (cs Constraints) Check(v *Version) bool {
+	for _, c := range cs {
+		if !c.Check(v) {
+			return false
+		}
+	}
+
+	return true
+}
+
+// Returns the string format of the constraints
+func (cs Constraints) String() string {
+	csStr := make([]string, len(cs))
+	for i, c := range cs {
+		csStr[i] = c.String()
+	}
+
+	return strings.Join(csStr, ",")
+}
+
+// Check tests if a constraint is validated by the given version.
+func (c *Constraint) Check(v *Version) bool {
+	return c.f(v, c.check)
+}
+
+func (c *Constraint) String() string {
+	return c.original
+}
+
+func parseSingle(v string) (*Constraint, error) {
+	matches := constraintRegexp.FindStringSubmatch(v)
+	if matches == nil {
+		return nil, fmt.Errorf("Malformed constraint: %s", v)
+	}
+
+	check, err := NewVersion(matches[2])
+	if err != nil {
+		return nil, err
+	}
+
+	return &Constraint{
+		f:        constraintOperators[matches[1]],
+		check:    check,
+		original: v,
+	}, nil
+}
+
+//-------------------------------------------------------------------
+// Constraint functions
+//-------------------------------------------------------------------
+
+func constraintEqual(v, c *Version) bool {
+	return v.Equal(c)
+}
+
+func constraintNotEqual(v, c *Version) bool {
+	return !v.Equal(c)
+}
+
+func constraintGreaterThan(v, c *Version) bool {
+	return v.Compare(c) == 1
+}
+
+func constraintLessThan(v, c *Version) bool {
+	return v.Compare(c) == -1
+}
+
+func constraintGreaterThanEqual(v, c *Version) bool {
+	return v.Compare(c) >= 0
+}
+
+func constraintLessThanEqual(v, c *Version) bool {
+	return v.Compare(c) <= 0
+}
+
+func constraintPessimistic(v, c *Version) bool {
+	// If the version being checked is naturally less than the constraint, then there
+	// is no way for the version to be valid against the constraint
+	if v.LessThan(c) {
+		return false
+	}
+	// We'll use this more than once, so grab the length now so it's a little cleaner
+	// to write the later checks
+	cs := len(c.segments)
+
+	// If the version being checked has less specificity than the constraint, then there
+	// is no way for the version to be valid against the constraint
+	if cs > len(v.segments) {
+		return false
+	}
+
+	// Check the segments in the constraint against those in the version. If the version
+	// being checked, at any point, does not have the same values in each index of the
+	// constraints segments, then it cannot be valid against the constraint.
+	for i := 0; i < c.si-1; i++ {
+		if v.segments[i] != c.segments[i] {
+			return false
+		}
+	}
+
+	// Check the last part of the segment in the constraint. If the version segment at
+	// this index is less than the constraints segment at this index, then it cannot
+	// be valid against the constraint
+	if c.segments[cs-1] > v.segments[cs-1] {
+		return false
+	}
+
+	// If nothing has rejected the version by now, it's valid
+	return true
+}
diff --git a/vendor/github.com/hashicorp/go-version/version.go b/vendor/github.com/hashicorp/go-version/version.go
new file mode 100644
index 000000000..dfe509caa
--- /dev/null
+++ b/vendor/github.com/hashicorp/go-version/version.go
@@ -0,0 +1,322 @@
+package version
+
+import (
+	"bytes"
+	"fmt"
+	"reflect"
+	"regexp"
+	"strconv"
+	"strings"
+)
+
+// The compiled regular expression used to test the validity of a version.
+var versionRegexp *regexp.Regexp
+
+// The raw regular expression string used for testing the validity
+// of a version.
+const VersionRegexpRaw string = `v?([0-9]+(\.[0-9]+)*?)` +
+	`(-?([0-9A-Za-z\-]+(\.[0-9A-Za-z\-]+)*))?` +
+	`(\+([0-9A-Za-z\-]+(\.[0-9A-Za-z\-]+)*))?` +
+	`?`
+
+// Version represents a single version.
+type Version struct {
+	metadata string
+	pre      string
+	segments []int64
+	si       int
+}
+
+func init() {
+	versionRegexp = regexp.MustCompile("^" + VersionRegexpRaw + "$")
+}
+
+// NewVersion parses the given version and returns a new
+// Version.
+func NewVersion(v string) (*Version, error) {
+	matches := versionRegexp.FindStringSubmatch(v)
+	if matches == nil {
+		return nil, fmt.Errorf("Malformed version: %s", v)
+	}
+	segmentsStr := strings.Split(matches[1], ".")
+	segments := make([]int64, len(segmentsStr))
+	si := 0
+	for i, str := range segmentsStr {
+		val, err := strconv.ParseInt(str, 10, 64)
+		if err != nil {
+			return nil, fmt.Errorf(
+				"Error parsing version: %s", err)
+		}
+
+		segments[i] = int64(val)
+		si++
+	}
+
+	// Even though we could support more than three segments, if we
+	// got less than three, pad it with 0s. This is to cover the basic
+	// default usecase of semver, which is MAJOR.MINOR.PATCH at the minimum
+	for i := len(segments); i < 3; i++ {
+		segments = append(segments, 0)
+	}
+
+	return &Version{
+		metadata: matches[7],
+		pre:      matches[4],
+		segments: segments,
+		si:       si,
+	}, nil
+}
+
+// Must is a helper that wraps a call to a function returning (*Version, error)
+// and panics if error is non-nil.
+func Must(v *Version, err error) *Version {
+	if err != nil {
+		panic(err)
+	}
+
+	return v
+}
+
+// Compare compares this version to another version. This
+// returns -1, 0, or 1 if this version is smaller, equal,
+// or larger than the other version, respectively.
+//
+// If you want boolean results, use the LessThan, Equal,
+// or GreaterThan methods.
+func (v *Version) Compare(other *Version) int {
+	// A quick, efficient equality check
+	if v.String() == other.String() {
+		return 0
+	}
+
+	segmentsSelf := v.Segments64()
+	segmentsOther := other.Segments64()
+
+	// If the segments are the same, we must compare on prerelease info
+	if reflect.DeepEqual(segmentsSelf, segmentsOther) {
+		preSelf := v.Prerelease()
+		preOther := other.Prerelease()
+		if preSelf == "" && preOther == "" {
+			return 0
+		}
+		if preSelf == "" {
+			return 1
+		}
+		if preOther == "" {
+			return -1
+		}
+
+		return comparePrereleases(preSelf, preOther)
+	}
+
+	// Get the highest specificity (hS), or if they're equal, just use segmentSelf length
+	lenSelf := len(segmentsSelf)
+	lenOther := len(segmentsOther)
+	hS := lenSelf
+	if lenSelf < lenOther {
+		hS = lenOther
+	}
+	// Compare the segments
+	// Because a constraint could have more/less specificity than the version it's
+	// checking, we need to account for a lopsided or jagged comparison
+	for i := 0; i < hS; i++ {
+		if i > lenSelf-1 {
+			// This means Self had the lower specificity
+			// Check to see if the remaining segments in Other are all zeros
+			if !allZero(segmentsOther[i:]) {
+				// if not, it means that Other has to be greater than Self
+				return -1
+			}
+			break
+		} else if i > lenOther-1 {
+			// this means Other had the lower specificity
+			// Check to see if the remaining segments in Self are all zeros -
+			if !allZero(segmentsSelf[i:]) {
+				//if not, it means that Self has to be greater than Other
+				return 1
+			}
+			break
+		}
+		lhs := segmentsSelf[i]
+		rhs := segmentsOther[i]
+		if lhs == rhs {
+			continue
+		} else if lhs < rhs {
+			return -1
+		}
+		// Otherwis, rhs was > lhs, they're not equal
+		return 1
+	}
+
+	// if we got this far, they're equal
+	return 0
+}
+
+func allZero(segs []int64) bool {
+	for _, s := range segs {
+		if s != 0 {
+			return false
+		}
+	}
+	return true
+}
+
+func comparePart(preSelf string, preOther string) int {
+	if preSelf == preOther {
+		return 0
+	}
+
+	selfNumeric := true
+	_, err := strconv.ParseInt(preSelf, 10, 64)
+	if err != nil {
+		selfNumeric = false
+	}
+
+	otherNumeric := true
+	_, err = strconv.ParseInt(preOther, 10, 64)
+	if err != nil {
+		otherNumeric = false
+	}
+
+	// if a part is empty, we use the other to decide
+	if preSelf == "" {
+		if otherNumeric {
+			return -1
+		}
+		return 1
+	}
+
+	if preOther == "" {
+		if selfNumeric {
+			return 1
+		}
+		return -1
+	}
+
+	if selfNumeric && !otherNumeric {
+		return -1
+	} else if !selfNumeric && otherNumeric {
+		return 1
+	} else if preSelf > preOther {
+		return 1
+	}
+
+	return -1
+}
+
+func comparePrereleases(v string, other string) int {
+	// the same pre release!
+	if v == other {
+		return 0
+	}
+
+	// split both pre releases for analyse their parts
+	selfPreReleaseMeta := strings.Split(v, ".")
+	otherPreReleaseMeta := strings.Split(other, ".")
+
+	selfPreReleaseLen := len(selfPreReleaseMeta)
+	otherPreReleaseLen := len(otherPreReleaseMeta)
+
+	biggestLen := otherPreReleaseLen
+	if selfPreReleaseLen > otherPreReleaseLen {
+		biggestLen = selfPreReleaseLen
+	}
+
+	// loop for parts to find the first difference
+	for i := 0; i < biggestLen; i = i + 1 {
+		partSelfPre := ""
+		if i < selfPreReleaseLen {
+			partSelfPre = selfPreReleaseMeta[i]
+		}
+
+		partOtherPre := ""
+		if i < otherPreReleaseLen {
+			partOtherPre = otherPreReleaseMeta[i]
+		}
+
+		compare := comparePart(partSelfPre, partOtherPre)
+		// if parts are equals, continue the loop
+		if compare != 0 {
+			return compare
+		}
+	}
+
+	return 0
+}
+
+// Equal tests if two versions are equal.
+func (v *Version) Equal(o *Version) bool {
+	return v.Compare(o) == 0
+}
+
+// GreaterThan tests if this version is greater than another version.
+func (v *Version) GreaterThan(o *Version) bool {
+	return v.Compare(o) > 0
+}
+
+// LessThan tests if this version is less than another version.
+func (v *Version) LessThan(o *Version) bool {
+	return v.Compare(o) < 0
+}
+
+// Metadata returns any metadata that was part of the version
+// string.
+//
+// Metadata is anything that comes after the "+" in the version.
+// For example, with "1.2.3+beta", the metadata is "beta".
+func (v *Version) Metadata() string {
+	return v.metadata
+}
+
+// Prerelease returns any prerelease data that is part of the version,
+// or blank if there is no prerelease data.
+//
+// Prerelease information is anything that comes after the "-" in the
+// version (but before any metadata). For example, with "1.2.3-beta",
+// the prerelease information is "beta".
+func (v *Version) Prerelease() string {
+	return v.pre
+}
+
+// Segments returns the numeric segments of the version as a slice of ints.
+//
+// This excludes any metadata or pre-release information. For example,
+// for a version "1.2.3-beta", segments will return a slice of
+// 1, 2, 3.
+func (v *Version) Segments() []int {
+	segmentSlice := make([]int, len(v.segments))
+	for i, v := range v.segments {
+		segmentSlice[i] = int(v)
+	}
+	return segmentSlice
+}
+
+// Segments64 returns the numeric segments of the version as a slice of int64s.
+//
+// This excludes any metadata or pre-release information. For example,
+// for a version "1.2.3-beta", segments will return a slice of
+// 1, 2, 3.
+func (v *Version) Segments64() []int64 {
+	return v.segments
+}
+
+// String returns the full version string included pre-release
+// and metadata information.
+func (v *Version) String() string {
+	var buf bytes.Buffer
+	fmtParts := make([]string, len(v.segments))
+	for i, s := range v.segments {
+		// We can ignore err here since we've pre-parsed the values in segments
+		str := strconv.FormatInt(s, 10)
+		fmtParts[i] = str
+	}
+	fmt.Fprintf(&buf, strings.Join(fmtParts, "."))
+	if v.pre != "" {
+		fmt.Fprintf(&buf, "-%s", v.pre)
+	}
+	if v.metadata != "" {
+		fmt.Fprintf(&buf, "+%s", v.metadata)
+	}
+
+	return buf.String()
+}
diff --git a/vendor/github.com/hashicorp/go-version/version_collection.go b/vendor/github.com/hashicorp/go-version/version_collection.go
new file mode 100644
index 000000000..cc888d43e
--- /dev/null
+++ b/vendor/github.com/hashicorp/go-version/version_collection.go
@@ -0,0 +1,17 @@
+package version
+
+// Collection is a type that implements the sort.Interface interface
+// so that versions can be sorted.
+type Collection []*Version
+
+func (v Collection) Len() int {
+	return len(v)
+}
+
+func (v Collection) Less(i, j int) bool {
+	return v[i].LessThan(v[j])
+}
+
+func (v Collection) Swap(i, j int) {
+	v[i], v[j] = v[j], v[i]
+}
diff --git a/vendor/vendor.json b/vendor/vendor.json
index 1b6634775..2074a3fbe 100644
--- a/vendor/vendor.json
+++ b/vendor/vendor.json
@@ -250,6 +250,12 @@
 			"revision": "ed905158d87462226a13fe39ddf685ea65f1c11f",
 			"revisionTime": "2016-12-16T18:43:04Z"
 		},
+		{
+			"checksumSHA1": "tUGxc7rfX0cmhOOUDhMuAZ9rWsA=",
+			"path": "github.com/hashicorp/go-version",
+			"revision": "03c5bf6be031b6dd45afec16b1cf94fc8938bc77",
+			"revisionTime": "2017-02-02T08:07:59Z"
+		},
 		{
 			"checksumSHA1": "7JBkp3EZoc0MSbiyWfzVhO4RYoY=",
 			"path": "github.com/hashicorp/hcl",