Add TransferIssue request

Signed-off-by: Eddie Zaneski <eddiezane@gmail.com>

prow/github/client.go

@@ -119,6 +119,7 @@ type IssueClient interface {
 	ListOpenIssues(org, repo string) ([]Issue, error)
 	GetIssue(org, repo string, number int) (*Issue, error)
 	EditIssue(org, repo string, number int, issue *Issue) (*Issue, error)
+	TransferIssue(org, dstRepo string, number int) (*TransferIssueMutation, error)
 }
 
 // PullRequestClient interface for pull request related API actions
@@ -2112,6 +2113,31 @@ func (c *client) EditIssue(org, repo string, number int, issue *Issue) (*Issue,
 	return &ret, nil
 }
 
+// TransferIssueMutation is a GraphQL mutation struct compatible with shurcooL/githubql's client
+type TransferIssueMutation struct {
+	TransferIssue struct {
+		Issue struct {
+			ResourcePath githubql.URI
+		}
+	} `graphql:"transferIssue(input: $input)"`
+}
+
+//// TransferIssue will move an issue from one repo to another in the same org.
+////
+//// See https://docs.github.com/en/graphql/reference/mutations#transferissue
+func (c *client) TransferIssue(org, dstRepo string, number int) (*TransferIssueMutation, error) {
+	durationLogger := c.log("TransferIssue", org, dstRepo, number)
+	defer durationLogger()
+
+	m := &TransferIssueMutation{}
+	input := githubql.TransferIssueInput{
+		IssueID: githubql.ID(number),
+		RepositoryID: githubql.ID(dstRepo),
+	}
+	err := c.gqlc.MutateWithGitHubAppsSupport(context.Background(), m, input, nil, org)
+	return m, err
+}
+
 // GetPullRequestPatch gets the patch version of a pull request.
 //
 // See https://developer.github.com/v3/media/#commits-commit-comparison-and-pull-requests