Get latest HashiCorp releases

Related to #560

In case a tool has a `URLTemplate` including
https://releases.hashicorp.com ,
it will fetch its latest release via the
https://checkpoint.hashicorp.com API.

At the moment, `terraform`, `vagrant`, and `packer` are being supported.

Signed-off-by: Yuval Goldberg <yuvigoldi@gmail.com>

pkg/get/get.go

@@ -3,8 +3,10 @@ package get
 import (
 	"bytes"
 	"crypto/tls"
+	"encoding/json"
 	"errors"
 	"fmt"
+	"io"
 	"io/ioutil"
 	"log"
 	"net"
@@ -22,6 +24,15 @@ var supportedArchitectures = [...]string{"x86_64", "arm", "amd64", "armv6l", "ar
 // githubTimeout expanded from the original 5 seconds due to #693
 var githubTimeout = time.Second * 10
 
+type HashiCorpProduct struct {
+	Product             string `json:"product"`
+	CurrentVersion      string `json:"current_version"`
+	CurrentRelease      int    `json:"current_release"`
+	CurrentDownloadURL  string `json:"current_download_url"`
+	CurrentChangelogURL string `json:"current_changelog_url"`
+	ProjectWebsite      string `json:"project_website"`
+}
+
 // Tool describes how to download a CLI tool from a binary
 // release - whether a single binary, or an archive.
 type Tool struct {
@@ -126,20 +137,34 @@ func (tool Tool) Head(uri string) (int, string, http.Header, error) {
 
 func (tool Tool) GetURL(os, arch, version string, quiet bool) (string, error) {
 
-	if len(version) == 0 &&
-		(len(tool.URLTemplate) == 0 || strings.Contains(tool.URLTemplate, "https://github.com/")) {
-		if !quiet {
-			log.Printf("Looking up version for %s", tool.Name)
-		}
+	if len(version) == 0 {
+		if len(tool.URLTemplate) == 0 || strings.Contains(tool.URLTemplate, "https://github.com/") {
+			if !quiet {
+				log.Printf("Looking up version for %s on GitHub", tool.Name)
+			}
 
-		v, err := FindGitHubRelease(tool.Owner, tool.Repo)
-		if err != nil {
-			return "", err
-		}
-		if !quiet {
-			log.Printf("Found: %s", v)
+			v, err := FindGitHubRelease(tool.Owner, tool.Repo)
+			if err != nil {
+				return "", err
+			}
+			if !quiet {
+				log.Printf("Found: %s", v)
+			}
+			version = v
+		} else if strings.Contains(tool.URLTemplate, "https://releases.hashicorp.com") {
+			if !quiet {
+				log.Printf("Looking up version for %s on HashiCorp", tool.Name)
+			}
+
+			v, err := FindHashiCorpRelease(tool.Name)
+			if err != nil {
+				return "", err
+			}
+			if !quiet {
+				log.Printf("Found: %s", v)
+			}
+			version = v
 		}
-		version = v
 	}
 
 	if len(tool.URLTemplate) > 0 {
@@ -213,6 +238,36 @@ func FindGitHubRelease(owner, repo string) (string, error) {
 	return version, nil
 }
 
+func FindHashiCorpRelease(name string) (string, error) {
+	url := fmt.Sprintf("https://checkpoint-api.hashicorp.com/v1/check/%s", name)
+	req, err := http.NewRequest(http.MethodGet, url, nil)
+	if err != nil {
+		return "", err
+	}
+
+	res, err := http.DefaultClient.Do(req)
+	if err != nil {
+		return "", err
+	}
+
+	if res.StatusCode != http.StatusOK {
+		return "", fmt.Errorf("unexpected status code: %d", res.StatusCode)
+	}
+	if res.Body == nil {
+		return "", fmt.Errorf("unexpected empty body")
+	}
+
+	defer res.Body.Close()
+	body, _ := io.ReadAll(res.Body)
+
+	var product HashiCorpProduct
+	if err = json.Unmarshal(body, &product); err != nil {
+		return "", err
+	}
+
+	return product.CurrentVersion, nil
+}
+
 func getBinaryURL(owner, repo, version, downloadName string) string {
 	if in := strings.Index(downloadName, "/"); in > -1 {
 		return fmt.Sprintf(

pkg/get/tools.go

@@ -659,7 +659,6 @@ https://github.com/inlets/inletsctl/releases/download/{{.Version}}/{{$fileName}}
 			Owner:       "hashicorp",
 			Repo:        "terraform",
 			Name:        "terraform",
-			Version:     "1.1.9",
 			Description: "Infrastructure as Code for major cloud providers.",
 			URLTemplate: `
 			{{$arch := ""}}
@@ -717,7 +716,6 @@ https://github.com/inlets/inletsctl/releases/download/{{.Version}}/{{$fileName}}
 			Owner:       "hashicorp",
 			Repo:        "vagrant",
 			Name:        "vagrant",
-			Version:     "2.2.19",
 			Description: "Tool for building and distributing development environments.",
 			URLTemplate: `{{$arch := .Arch}}
 
@@ -739,7 +737,6 @@ https://releases.hashicorp.com/{{.Name}}/{{.Version}}/{{.Name}}_{{.Version}}_{{$
 			Owner:       "hashicorp",
 			Repo:        "packer",
 			Name:        "packer",
-			Version:     "1.8.0",
 			Description: "Build identical machine images for multiple platforms from a single source configuration.",
 			URLTemplate: `
 			{{$arch := ""}}