handle pull_request events separately (#10)

use PullRequests.ListFiles to retrieve all files changed since the pull request
was opened

plugin/get.go

@@ -2,13 +2,19 @@ package plugin
 
 import (
 	"context"
+	"regexp"
+	"strconv"
 
 	"github.com/drone/drone-go/drone"
 
 	"github.com/google/go-github/github"
 	"golang.org/x/oauth2"
 )
 
+// regular expression to extract the pull request number
+// from the git ref (e.g. refs/pulls/{d}/head)
+var re = regexp.MustCompile("\\d+")
+
 func getFilesChanged(repo drone.Repo, build drone.Build, token string) ([]string, error) {
 	newctx := context.Background()
 	ts := oauth2.StaticTokenSource(
@@ -19,18 +25,44 @@ func getFilesChanged(repo drone.Repo, build drone.Build, token string) ([]string
 	client := github.NewClient(tc)
 
 	var commitFiles []github.CommitFile
-	if build.Before == "" || build.Before == "0000000000000000000000000000000000000000" {
-		response, _, err := client.Repositories.GetCommit(newctx, repo.Namespace, repo.Name, build.After)
+
+	if build.Event == "pull_request" {
+		s := re.FindString(build.Ref)
+		d, _ := strconv.Atoi(s)
+
+		listOpts := &github.ListOptions{
+			Page:    1,
+			PerPage: 300,
+		}
+		allFiles := []*github.CommitFile{}
+
+		for {
+			cfs, resp, err := client.PullRequests.ListFiles(newctx, repo.Namespace, repo.Name, d, listOpts)
+			if err != nil {
+				return nil, err
+			}
+
+			allFiles = append(allFiles, cfs...)
+			if resp.NextPage == 0 {
+				break
+			}
+			listOpts.Page = resp.NextPage
+		}
+		for _, file := range allFiles {
+			commitFiles = append(commitFiles, *file)
+		}
+	} else if build.Before == "" || build.Before == "0000000000000000000000000000000000000000" {
+		rc, _, err := client.Repositories.GetCommit(newctx, repo.Namespace, repo.Name, build.After)
 		if err != nil {
 			return nil, err
 		}
-		commitFiles = response.Files
+		commitFiles = rc.Files
 	} else {
-		response, _, err := client.Repositories.CompareCommits(newctx, repo.Namespace, repo.Name, build.Before, build.After)
+		cc, _, err := client.Repositories.CompareCommits(newctx, repo.Namespace, repo.Name, build.Before, build.After)
 		if err != nil {
 			return nil, err
 		}
-		commitFiles = response.Files
+		commitFiles = cc.Files
 	}
 
 	var files []string