Add basic lookup functions

command/pr.go

@@ -944,16 +944,14 @@ func prProjectList(pr api.PullRequest) string {
 	return list
 }
 
-var prURLRE = regexp.MustCompile(`^https://github\.com/([^/]+)/([^/]+)/pull/(\d+)`)
-
-func prFromURL(arg string) (string, ghrepo.Interface) {
+func prFromURL_old(arg string) (string, ghrepo.Interface) {
 	if m := prURLRE.FindStringSubmatch(arg); m != nil {
 		return m[3], ghrepo.New(m[1], m[2])
 	}
 	return "", nil
 }
 
-func prFromArg(apiClient *api.Client, baseRepo ghrepo.Interface, arg string) (*api.PullRequest, error) {
+func prFromArg_old(apiClient *api.Client, baseRepo ghrepo.Interface, arg string) (*api.PullRequest, error) {
 	if prNumber, err := strconv.Atoi(strings.TrimPrefix(arg, "#")); err == nil {
 		return api.PullRequestByNumber(apiClient, baseRepo, prNumber)
 	}

command/pr_lookup.go

@@ -0,0 +1,111 @@
+package command
+
+import (
+	"fmt"
+	"regexp"
+	"strconv"
+	"strings"
+
+	"github.com/cli/cli/api"
+	"github.com/cli/cli/context"
+	"github.com/cli/cli/git"
+	"github.com/cli/cli/internal/ghrepo"
+)
+
+func prFromArguments(ctx context.Context, repo ghrepo.Interface, args []string) (*api.PullRequest, error) {
+	apiClient, err := apiClientForContext(ctx)
+	if err != nil {
+		return nil, err
+	}
+
+	if len(args) == 0 {
+		return prForCurrentBranch(ctx, repo)
+	}
+
+	prString := args[0]
+
+	// First check to see if the prString is a url
+	pr, err := prFromURL(ctx, repo, prString)
+	if pr != nil || err != nil {
+		return pr, err
+	}
+
+	// Next see if the prString is a number and use that to look up the url
+	pr, err = prFromNumberString(ctx, repo, prString)
+	if pr != nil || err != nil {
+		return pr, err
+	}
+
+	// Last see if it is a branch name
+	pr, err = api.PullRequestForBranch(apiClient, repo, "", prString)
+	return pr, err
+}
+
+func prFromNumberString(ctx context.Context, repo ghrepo.Interface, s string) (*api.PullRequest, error) {
+	apiClient, err := apiClientForContext(ctx)
+	if err != nil {
+		return nil, err
+	}
+
+	if prNumber, err := strconv.Atoi(strings.TrimPrefix(s, "#")); err == nil {
+		return api.PullRequestByNumber(apiClient, repo, prNumber)
+	}
+
+	return nil, nil
+}
+
+func prFromURL(ctx context.Context, repo ghrepo.Interface, s string) (*api.PullRequest, error) {
+	var r = regexp.MustCompile(`^https://github\.com/([^/]+)/([^/]+)/pull/(\d+)`)
+	if m := r.FindStringSubmatch(s); m != nil {
+		prNumberString := m[3]
+		return prFromNumberString(ctx, repo, prNumberString)
+	}
+
+	return nil, nil
+}
+
+func prForCurrentBranch(ctx context.Context, repo ghrepo.Interface) (*api.PullRequest, error) {
+	apiClient, err := apiClientForContext(ctx)
+	if err != nil {
+		return nil, err
+	}
+
+	prHeadRef, err := ctx.Branch()
+	if err != nil {
+		return nil, err
+	}
+
+	branchConfig := git.ReadBranchConfig(prHeadRef)
+
+	// the branch is configured to merge a special PR head ref
+	prHeadRE := regexp.MustCompile(`^refs/pull/(\d+)/head$`)
+	if m := prHeadRE.FindStringSubmatch(branchConfig.MergeRef); m != nil {
+		return prFromNumberString(ctx, repo, m[1])
+	}
+
+	var branchOwner string
+	if branchConfig.RemoteURL != nil {
+		// the branch merges from a remote specified by URL
+		if r, err := ghrepo.FromURL(branchConfig.RemoteURL); err == nil {
+			branchOwner = r.RepoOwner()
+		}
+	} else if branchConfig.RemoteName != "" {
+		// the branch merges from a remote specified by name
+		rem, _ := ctx.Remotes()
+		if r, err := rem.FindByName(branchConfig.RemoteName); err == nil {
+			branchOwner = r.RepoOwner()
+		}
+	}
+
+	if branchOwner == "" {
+		if strings.HasPrefix(branchConfig.MergeRef, "refs/heads/") {
+			prHeadRef = strings.TrimPrefix(branchConfig.MergeRef, "refs/heads/")
+		}
+		// prepend `OWNER:` if this branch is pushed to a fork
+		if !strings.EqualFold(branchOwner, repo.RepoOwner()) {
+			prHeadRef = fmt.Sprintf("%s:%s", branchOwner, prHeadRef)
+		}
+	}
+
+	return api.PullRequestForBranch(apiClient, repo, "", prHeadRef)
+}