Add test for mutually exclusive flags

Co-Authored-By: Nate Smith <vilmibm@neongrid.space>

command/pr.go

@@ -1,6 +1,7 @@
 package command
 
 import (
+	"errors"
 	"fmt"
 	"io"
 	"os"
@@ -479,7 +480,24 @@ func prMerge(cmd *cobra.Command, args []string) error {
 		return nil
 	}
 
-	isInteractive := !cmd.Flags().Changed("rebase") && !cmd.Flags().Changed("squash") && !cmd.Flags().Changed("merge")
+	// Ensure only one merge method is specified
+	found := 0
+	isInteractive := false
+	if cmd.Flags().Changed("merge") {
+		found++
+	}
+	if cmd.Flags().Changed("rebase") {
+		found++
+	}
+	if cmd.Flags().Changed("squash") {
+		found++
+	}
+	if found == 0 {
+		isInteractive = true
+	} else if found > 1 {
+		return errors.New("expected exactly one of --merge, --rebase, or --squash")
+	}
+
 	if isInteractive {
 		mergeMethod, deleteBranch, err = prInteractiveMerge()
 		if err != nil {

command/pr_test.go

@@ -996,6 +996,15 @@ func TestPrMerge(t *testing.T) {
 		stubResponse{200, bytes.NewBufferString(`{"id": "THE-ID"}`)},
 	)
 
+	cs, cmdTeardown := test.InitCmdStubber()
+	defer cmdTeardown()
+
+	cs.Stub("branch.blueberries.remote origin\nbranch.blueberries.merge refs/heads/blueberries") // git config --get-regexp ^branch\.master\.(remote|merge)
+	cs.Stub("")                                                                                  // git config --get-regexp ^branch\.blueberries\.(remote|merge)$
+	cs.Stub("")                                                                                  // git symbolic-ref --quiet --short HEAD
+	cs.Stub("")                                                                                  // git checkout master
+	cs.Stub("")
+
 	output, err := RunCommand("pr merge 1 --merge")
 	if err != nil {
 		t.Fatalf("error running command `pr merge`: %v", err)
@@ -1159,3 +1168,17 @@ func TestPRMerge_interactive(t *testing.T) {
 
 	test.ExpectLines(t, output.String(), "Merged pull request #3", "Deleted local branch")
 }
+
+func TestPrMerge_multipleMergeMethods(t *testing.T) {
+	initWithStubs("master",
+		stubResponse{200, bytes.NewBufferString(`{ "data": { "repository": {
+			"pullRequest": { "number": 1, "closed": false, "state": "OPEN"}
+		} } }`)},
+		stubResponse{200, bytes.NewBufferString(`{"id": "THE-ID"}`)},
+	)
+
+	_, err := RunCommand("pr merge 1 --merge --squash")
+	if err == nil {
+		t.Fatal("expected error running `pr merge` with multiple merge methods")
+	}
+}