List linked branches works

api/queries_branch_issue_reference.go

@@ -1,5 +1,7 @@
 package api
 
+import "github.com/cli/cli/v2/internal/ghrepo"
+
 type BranchIssueReference struct {
 	ID         string
 	BranchName string
@@ -58,6 +60,61 @@ func CreateBranchIssueReference(client *Client, repo *Repository, params map[str
 
 }
 
+func ListLinkedBranches(client *Client, repo ghrepo.Interface, issueNumber int) ([]string, error) {
+	// query uses name and owner
+	query := `
+	query BranchIssueReferenceListLinkedBranches($repositoryName: String!, $repositoryOwner: String!, $issueNumber: Int!) {
+		repository(name: $repositoryName, owner: $repositoryOwner) {
+			issue(number: $issueNumber) {
+				linkedBranches(first: 30) {
+					edges {
+						node {
+							ref {
+								name
+							}
+						}
+					}
+				}
+			}
+		}
+	}
+	`
+	variables := map[string]interface{}{
+		"repositoryName":  repo.RepoName(),
+		"repositoryOwner": repo.RepoOwner(),
+		"issueNumber":     issueNumber,
+	}
+
+	result := struct {
+		Repository struct {
+			Issue struct {
+				LinkedBranches struct {
+					Edges []struct {
+						Node struct {
+							Ref struct {
+								Name string
+							}
+						}
+					}
+				}
+			}
+		}
+	}{}
+
+	err := client.GraphQL(repo.RepoHost(), query, variables, &result)
+	var branchNames []string
+	if err != nil {
+		return branchNames, err
+	}
+
+	for _, edge := range result.Repository.Issue.LinkedBranches.Edges {
+		branchNames = append(branchNames, edge.Node.Ref.Name)
+	}
+
+	return branchNames, nil
+
+}
+
 func FindBaseOid(client *Client, repo *Repository, ref string) (string, string, error) {
 	query := `
 	query BranchIssueReferenceFindBaseOid($repositoryName: String!, $repositoryOwner: String!, $ref: String!) {

pkg/cmd/issue/develop/develop.go

@@ -24,11 +24,12 @@ type DevelopOptions struct {
 	BaseRepo   func() (ghrepo.Interface, error)
 	Remotes    func() (context.Remotes, error)
 
-	IssueRepo     string
-	IssueSelector string
-	Name          string
-	BaseBranch    string
-	Checkout      bool
+	IssueRepoSelector string
+	IssueSelector     string
+	Name              string
+	BaseBranch        string
+	Checkout          bool
+	List              bool
 }
 
 func NewCmdDevelop(f *cmdutil.Factory, runF func(*DevelopOptions) error) *cobra.Command {
@@ -45,23 +46,28 @@ func NewCmdDevelop(f *cmdutil.Factory, runF func(*DevelopOptions) error) *cobra.
 		Short: "Manage linked branches for an issue",
 		Example: heredoc.Doc(`
 			$ gh issue develop --list 123 # list branches for issue 123
-			$ gh issue develop --issue-repo "github/cli" 123 list branches for issue 123 in repo "github/cli"
+			$ gh issue develop --list --issue-repo "github/cli" 123 list branches for issue 123 in repo "github/cli"
+			$ gh issue develop --list https://github.com/github/cli/issues/123 # list branches for issue 123 in repo "github/cli"
 			$ gh issue develop 123 --name "my-branch" --head main
 			$ gh issue develop 123 --checkout # checkout the branch for issue 123 after creating it
 			`),
-		Args: cmdutil.ExactArgs(1, "issue number is required"),
+		Args: cmdutil.ExactArgs(1, "issue number or url is required"),
 		RunE: func(cmd *cobra.Command, args []string) error {
 			if runF != nil {
 				return runF(opts)
 			}
 			opts.IssueSelector = args[0]
+			if opts.List {
+				return developRunList(opts)
+			}
 			return developRun(opts)
 		},
 	}
 	fl := cmd.Flags()
 	fl.StringVarP(&opts.BaseBranch, "base-branch", "b", "", "Name of the base branch")
 	fl.BoolVarP(&opts.Checkout, "checkout", "c", false, "Checkout the branch after creating it")
-	fl.StringVarP(&opts.IssueRepo, "issue-repo", "i", "", "Name or URL of the issue's repository")
+	fl.StringVarP(&opts.IssueRepoSelector, "issue-repo", "i", "", "Name or URL of the issue's repository")
+	fl.BoolVarP(&opts.List, "list", "l", false, "List branches for the issue")
 	fl.StringVarP(&opts.Name, "name", "n", "", "Name of the branch to create")
 	return cmd
 }
@@ -120,6 +126,58 @@ func developRun(opts *DevelopOptions) (err error) {
 	return
 }
 
+func developRunList(opts *DevelopOptions) (err error) {
+	httpClient, err := opts.HttpClient()
+	if err != nil {
+		return err
+	}
+
+	apiClient := api.NewClientFromHTTP(httpClient)
+	baseRepo, err := opts.BaseRepo()
+	if err != nil {
+		return err
+	}
+
+	opts.IO.StartProgressIndicator()
+	var issueRepo ghrepo.Interface
+	if opts.IssueRepoSelector != "" {
+		issueRepo, err = ghrepo.FromFullNameWithHost(opts.IssueRepoSelector, baseRepo.RepoHost())
+		if err != nil {
+			return err
+		}
+	}
+
+	targetRepo := baseRepo
+	if issueRepo != nil {
+		targetRepo = issueRepo
+	}
+	issueNumber, issueRepo, err := shared.IssueNumberAndRepoFromArg(opts.IssueSelector, targetRepo)
+	if err != nil {
+		return err
+	}
+
+	branches, err := api.ListLinkedBranches(apiClient, issueRepo, issueNumber)
+	if err != nil {
+		return err
+	}
+
+	opts.IO.StopProgressIndicator()
+	if len(branches) == 0 {
+		return cmdutil.NewNoResultsError(fmt.Sprintf("no linked branches found for %s/%s#%d", issueRepo.RepoOwner(), issueRepo.RepoName(), issueNumber))
+	}
+
+	if opts.IO.IsStdoutTTY() {
+		fmt.Fprintf(opts.IO.Out, "\nShowing linked branches for %s/%s#%d\n\n", issueRepo.RepoOwner(), issueRepo.RepoName(), issueNumber)
+	}
+
+	for _, branch := range branches {
+		fmt.Fprintf(opts.IO.Out, "%s\n", branch)
+	}
+
+	return nil
+
+}
+
 func checkoutBranch(opts *DevelopOptions, baseRepo ghrepo.Interface, checkoutBranch string) (err error) {
 
 	remotes, err := opts.Remotes()

pkg/cmd/issue/list/http.go

@@ -22,6 +22,7 @@ func listIssues(client *api.Client, repo ghrepo.Interface, filters prShared.Filt
 	}
 
 	fragments := fmt.Sprintf("fragment issue on Issue {%s}", api.PullRequestGraphQL(filters.Fields))
+	// TODO try to paginate like this
 	query := fragments + `
 	query IssueList($owner: String!, $repo: String!, $limit: Int, $endCursor: String, $states: [IssueState!] = OPEN, $assignee: String, $author: String, $mention: String) {
 		repository(owner: $owner, name: $repo) {

pkg/cmd/issue/shared/lookup.go

@@ -60,6 +60,26 @@ func issueMetadataFromURL(s string) (int, ghrepo.Interface) {
 	return issueNumber, repo
 }
 
+//TODO: Returns the issue number and base repo if the issue URL is provided, falling back to the
+// supplied repo if the base repo is not specified in the URL.
+func IssueNumberAndRepoFromArg(arg string, fallbackRepo ghrepo.Interface) (int, ghrepo.Interface, error) {
+	issueNumber, baseRepo := issueMetadataFromURL(arg)
+
+	if issueNumber == 0 {
+		var err error
+		issueNumber, err = strconv.Atoi(strings.TrimPrefix(arg, "#"))
+		if err != nil {
+			return 0, nil, fmt.Errorf("invalid issue format: %q", arg)
+		}
+	}
+
+	if baseRepo == nil {
+		baseRepo = fallbackRepo
+	}
+
+	return issueNumber, baseRepo, nil
+}
+
 type PartialLoadError struct {
 	error
 }