add command file with pr resolution

command/pr_diff.go

@@ -0,0 +1,75 @@
+package command
+
+import (
+	"errors"
+	"fmt"
+	"strconv"
+	"strings"
+
+	"github.com/cli/cli/api"
+	"github.com/spf13/cobra"
+)
+
+var prDiffCmd = &cobra.Command{
+	Use:   "diff {<number> | <url>}",
+	Short: "View a pull request's changes.",
+	RunE:  prDiff,
+}
+
+func init() {
+	prDiffCmd.Flags().StringP("color", "c", "auto", "Whether or not to output color: {always|never|auto}")
+
+	prCmd.AddCommand(prDiffCmd)
+}
+
+func prDiff(cmd *cobra.Command, args []string) error {
+	ctx := contextForCommand(cmd)
+	apiClient, err := apiClientForContext(ctx)
+	if err != nil {
+		return err
+	}
+
+	baseRepo, err := determineBaseRepo(apiClient, cmd, ctx)
+	if err != nil {
+		return fmt.Errorf("could not determine base repo: %w", err)
+	}
+
+	var prNum int
+	branchWithOwner := ""
+
+	if len(args) == 0 {
+		prNum, branchWithOwner, err = prSelectorForCurrentBranch(ctx, baseRepo)
+		if err != nil {
+			return fmt.Errorf("could not query for pull request for current branch: %w", err)
+		}
+	} else {
+		prArg, repo := prFromURL(args[0])
+		if repo != nil {
+			baseRepo = repo
+		} else {
+			prArg = strings.TrimPrefix(args[0], "#")
+		}
+		prNum, err = strconv.Atoi(prArg)
+		if err != nil {
+			return errors.New("could not parse pull request argument")
+		}
+	}
+
+	var pr *api.PullRequest
+	if prNum > 0 {
+		pr, err = api.PullRequestByNumber(apiClient, baseRepo, prNum)
+		if err != nil {
+			return fmt.Errorf("could not find pull request: %w", err)
+		}
+	} else {
+		pr, err = api.PullRequestForBranch(apiClient, baseRepo, "", branchWithOwner)
+		if err != nil {
+			return fmt.Errorf("could not find pull request: %w", err)
+		}
+		prNum = pr.Number
+	}
+
+	fmt.Println(pr.Title)
+
+	return nil
+}