Add support for downloading source artifacts from Github release

This adds support for retrieving the tarball or zip source artifact from a
Github release. This is done through defining a
"params.include_source_tarball" or "params.include_source_zip" boolean setting.

With this, the resource will download the respective source artfact into the
target directory as either "source.tar.gz" or "source.zip".

README.md

@@ -67,6 +67,12 @@ Also creates the following files:
 * `globs`: *Optional.* A list of globs for files that will be downloaded from
   the release. If not specified, all assets will be fetched.
 
+* `include_source_tarball`: *Optional.* Enables downloading of the source
+  artifact tarball for the release as `source.tar.gz`. Defaults to `false`.
+
+* `include_source_zip`: *Optional.* Enables downloading of the source
+  artifact zip for the release as `source.zip`. Defaults to `false`.
+
 ### `out`: Publish a release.
 
 Given a name specified in `name`, a body specified in `body`, and the tag to use

fakes/fake_git_hub.go

@@ -3,6 +3,7 @@ package fakes
 
 import (
 	"io"
+	"net/url"
 	"os"
 	"sync"
 
@@ -81,6 +82,24 @@ type FakeGitHub struct {
 		result1 io.ReadCloser
 		result2 error
 	}
+	GetTarballLinkStub        func(tag string) (*url.URL, error)
+	getTarballLinkMutex       sync.RWMutex
+	getTarballLinkArgsForCall []struct {
+		tag string
+	}
+	getTarballLinkReturns struct {
+		result1 *url.URL
+		result2 error
+	}
+	GetZipballLinkStub        func(tag string) (*url.URL, error)
+	getZipballLinkMutex       sync.RWMutex
+	getZipballLinkArgsForCall []struct {
+		tag string
+	}
+	getZipballLinkReturns struct {
+		result1 *url.URL
+		result2 error
+	}
 }
 
 func (fake *FakeGitHub) ListReleases() ([]github.RepositoryRelease, error) {
@@ -339,4 +358,70 @@ func (fake *FakeGitHub) DownloadReleaseAssetReturns(result1 io.ReadCloser, resul
 	}{result1, result2}
 }
 
+func (fake *FakeGitHub) GetTarballLink(tag string) (*url.URL, error) {
+	fake.getTarballLinkMutex.Lock()
+	fake.getTarballLinkArgsForCall = append(fake.getTarballLinkArgsForCall, struct {
+		tag string
+	}{tag})
+	fake.getTarballLinkMutex.Unlock()
+	if fake.GetReleaseByTagStub != nil {
+		return fake.GetTarballLinkStub(tag)
+	} else {
+		return fake.getTarballLinkReturns.result1, fake.getTarballLinkReturns.result2
+	}
+}
+
+func (fake *FakeGitHub) GetTarballLinkCallCount() int {
+	fake.getTarballLinkMutex.RLock()
+	defer fake.getTarballLinkMutex.RUnlock()
+	return len(fake.getTarballLinkArgsForCall)
+}
+
+func (fake *FakeGitHub) GetTarballLinkArgsForCall(i int) string {
+	fake.getTarballLinkMutex.RLock()
+	defer fake.getTarballLinkMutex.RUnlock()
+	return fake.getTarballLinkArgsForCall[i].tag
+}
+
+func (fake *FakeGitHub) GetTarballLinkReturns(result1 *url.URL, result2 error) {
+	fake.GetTarballLinkStub = nil
+	fake.getTarballLinkReturns = struct {
+		result1 *url.URL
+		result2 error
+	}{result1, result2}
+}
+
+func (fake *FakeGitHub) GetZipballLink(tag string) (*url.URL, error) {
+	fake.getZipballLinkMutex.Lock()
+	fake.getZipballLinkArgsForCall = append(fake.getZipballLinkArgsForCall, struct {
+		tag string
+	}{tag})
+	fake.getZipballLinkMutex.Unlock()
+	if fake.GetReleaseByTagStub != nil {
+		return fake.GetZipballLinkStub(tag)
+	} else {
+		return fake.getZipballLinkReturns.result1, fake.getZipballLinkReturns.result2
+	}
+}
+
+func (fake *FakeGitHub) GetZipballLinkCallCount() int {
+	fake.getZipballLinkMutex.RLock()
+	defer fake.getZipballLinkMutex.RUnlock()
+	return len(fake.getZipballLinkArgsForCall)
+}
+
+func (fake *FakeGitHub) GetZipballLinkArgsForCall(i int) string {
+	fake.getZipballLinkMutex.RLock()
+	defer fake.getZipballLinkMutex.RUnlock()
+	return fake.getZipballLinkArgsForCall[i].tag
+}
+
+func (fake *FakeGitHub) GetZipballLinkReturns(result1 *url.URL, result2 error) {
+	fake.GetZipballLinkStub = nil
+	fake.getZipballLinkReturns = struct {
+		result1 *url.URL
+		result2 error
+	}{result1, result2}
+}
+
 var _ resource.GitHub = new(FakeGitHub)

github.go

@@ -23,6 +23,9 @@ type GitHub interface {
 	UploadReleaseAsset(release github.RepositoryRelease, name string, file *os.File) error
 	DeleteReleaseAsset(asset github.ReleaseAsset) error
 	DownloadReleaseAsset(asset github.ReleaseAsset) (io.ReadCloser, error)
+
+	GetTarballLink(tag string) (*url.URL, error)
+	GetZipballLink(tag string) (*url.URL, error)
 }
 
 type GitHubClient struct {
@@ -170,3 +173,23 @@ func (g *GitHubClient) DownloadReleaseAsset(asset github.ReleaseAsset) (io.ReadC
 
 	return res, err
 }
+
+func (g *GitHubClient) GetTarballLink(tag string) (*url.URL, error) {
+	opt := &github.RepositoryContentGetOptions{Ref: tag}
+	u, res, err := g.client.Repositories.GetArchiveLink(g.user, g.repository, github.Tarball, opt)
+	if err != nil {
+		return nil, err
+	}
+	res.Body.Close()
+	return u, nil
+}
+
+func (g *GitHubClient) GetZipballLink(tag string) (*url.URL, error) {
+	opt := &github.RepositoryContentGetOptions{Ref: tag}
+	u, res, err := g.client.Repositories.GetArchiveLink(g.user, g.repository, github.Zipball, opt)
+	if err != nil {
+		return nil, err
+	}
+	res.Body.Close()
+	return u, nil
+}

in_command.go

@@ -5,6 +5,7 @@ import (
 	"fmt"
 	"io"
 	"io/ioutil"
+	"net/http"
 	"os"
 	"path/filepath"
 
@@ -84,12 +85,34 @@ func (c *InCommand) Run(destDir string, request InRequest) (InResponse, error) {
 
 		fmt.Fprintf(c.writer, "downloading asset: %s\n", *asset.Name)
 
-		err := c.downloadFile(asset, path)
+		err := c.downloadAsset(asset, path)
 		if err != nil {
 			return InResponse{}, err
 		}
 	}
 
+	if request.Params.IncludeSourceTarball {
+		u, err := c.github.GetTarballLink(request.Version.Tag)
+		if err != nil {
+			return InResponse{}, err
+		}
+		fmt.Fprintln(c.writer, "downloading source tarball to source.tar.gz")
+		if err := c.downloadFile(u.String(), filepath.Join(destDir, "source.tar.gz")); err != nil {
+			return InResponse{}, err
+		}
+	}
+
+	if request.Params.IncludeSourceZip {
+		u, err := c.github.GetZipballLink(request.Version.Tag)
+		if err != nil {
+			return InResponse{}, err
+		}
+		fmt.Fprintln(c.writer, "downloading source zip to source.zip")
+		if err := c.downloadFile(u.String(), filepath.Join(destDir, "source.zip")); err != nil {
+			return InResponse{}, err
+		}
+	}
+
 	return InResponse{
 		Version: Version{
 			Tag: *foundRelease.TagName,
@@ -98,7 +121,7 @@ func (c *InCommand) Run(destDir string, request InRequest) (InResponse, error) {
 	}, nil
 }
 
-func (c *InCommand) downloadFile(asset github.ReleaseAsset, destPath string) error {
+func (c *InCommand) downloadAsset(asset github.ReleaseAsset, destPath string) error {
 	out, err := os.Create(destPath)
 	if err != nil {
 		return err
@@ -118,3 +141,28 @@ func (c *InCommand) downloadFile(asset github.ReleaseAsset, destPath string) err
 
 	return nil
 }
+
+func (c *InCommand) downloadFile(url, destPath string) error {
+	out, err := os.Create(destPath)
+	if err != nil {
+		return err
+	}
+	defer out.Close()
+
+	resp, err := http.Get(url)
+	if err != nil {
+		return err
+	}
+	defer resp.Body.Close()
+
+	if resp.StatusCode != http.StatusOK {
+		return fmt.Errorf("failed to download file: HTTP status %d: %s", resp.StatusCode, resp.Status)
+	}
+
+	_, err = io.Copy(out, resp.Body)
+	if err != nil {
+		return err
+	}
+
+	return nil
+}

resources.go

@@ -21,6 +21,8 @@ type InRequest struct {
 
 type InParams struct {
 	Globs                []string `json:"globs"`
+	IncludeSourceTarball bool     `json:"include_source_tarball"`
+	IncludeSourceZip     bool     `json:"include_source_zip"`
 }
 
 type InResponse struct {