From a89fa1ebed812c0941868da7bd370e91e82dd932 Mon Sep 17 00:00:00 2001
From: Neel Redkar <neel.redkar@gmail.com>
Date: Thu, 24 Sep 2020 16:26:35 -0700
Subject: [PATCH] add ability to force checkout

---
 pkg/cmd/pr/checkout/checkout.go      | 26 +++++++++++++++--
 pkg/cmd/pr/checkout/checkout_test.go | 42 ++++++++++++++++++++++++++++
 2 files changed, 65 insertions(+), 3 deletions(-)

diff --git a/pkg/cmd/pr/checkout/checkout.go b/pkg/cmd/pr/checkout/checkout.go
index 34db96f87..fc5002b0f 100644
--- a/pkg/cmd/pr/checkout/checkout.go
+++ b/pkg/cmd/pr/checkout/checkout.go
@@ -30,6 +30,7 @@ type CheckoutOptions struct {
 
 	SelectorArg       string
 	RecurseSubmodules bool
+	Force             bool
 }
 
 func NewCmdCheckout(f *cmdutil.Factory, runF func(*CheckoutOptions) error) *cobra.Command {
@@ -61,6 +62,7 @@ func NewCmdCheckout(f *cmdutil.Factory, runF func(*CheckoutOptions) error) *cobr
 	}
 
 	cmd.Flags().BoolVarP(&opts.RecurseSubmodules, "recurse-submodules", "", false, "Update all active submodules (recursively)")
+	cmd.Flags().BoolVarP(&opts.Force, "force", "f", false, "Force merge into local branch")
 
 	return cmd
 }
@@ -116,7 +118,12 @@ func checkoutRun(opts *CheckoutOptions) error {
 		// local branch already exists
 		if _, err := git.ShowRefs("refs/heads/" + newBranchName); err == nil {
 			cmdQueue = append(cmdQueue, []string{"git", "checkout", newBranchName})
-			cmdQueue = append(cmdQueue, []string{"git", "merge", "--ff-only", fmt.Sprintf("refs/remotes/%s", remoteBranch)})
+			// If forced reset to remote
+			if opts.Force {
+				cmdQueue = append(cmdQueue, []string{"git", "reset", "--hard", fmt.Sprintf("refs/remotes/%s", remoteBranch)})
+			} else {
+				cmdQueue = append(cmdQueue, []string{"git", "merge", "--ff-only", fmt.Sprintf("refs/remotes/%s", remoteBranch)})
+			}
 		} else {
 			cmdQueue = append(cmdQueue, []string{"git", "checkout", "-b", newBranchName, "--no-track", remoteBranch})
 			cmdQueue = append(cmdQueue, []string{"git", "config", fmt.Sprintf("branch.%s.remote", newBranchName), headRemote.Name})
@@ -139,11 +146,24 @@ func checkoutRun(opts *CheckoutOptions) error {
 		ref := fmt.Sprintf("refs/pull/%d/head", pr.Number)
 		if newBranchName == currentBranch {
 			// PR head matches currently checked out branch
+
 			cmdQueue = append(cmdQueue, []string{"git", "fetch", baseURLOrName, ref})
-			cmdQueue = append(cmdQueue, []string{"git", "merge", "--ff-only", "FETCH_HEAD"})
+
+			// If forced reset to remote
+			if opts.Force {
+				cmdQueue = append(cmdQueue, []string{"git", "reset", "--hard", "FETCH_HEAD"})
+			} else {
+				cmdQueue = append(cmdQueue, []string{"git", "merge", "--ff-only", "FETCH_HEAD"})
+			}
 		} else {
 			// create a new branch
-			cmdQueue = append(cmdQueue, []string{"git", "fetch", baseURLOrName, fmt.Sprintf("%s:%s", ref, newBranchName)})
+
+			// If forced reset to remote
+			if opts.Force {
+				cmdQueue = append(cmdQueue, []string{"git", "fetch", baseURLOrName, fmt.Sprintf("%s:%s", ref, newBranchName), "--force"})
+			} else {
+				cmdQueue = append(cmdQueue, []string{"git", "fetch", baseURLOrName, fmt.Sprintf("%s:%s", ref, newBranchName)})
+			}
 			cmdQueue = append(cmdQueue, []string{"git", "checkout", newBranchName})
 		}
 
diff --git a/pkg/cmd/pr/checkout/checkout_test.go b/pkg/cmd/pr/checkout/checkout_test.go
index 5042c0c84..aa68d0b9d 100644
--- a/pkg/cmd/pr/checkout/checkout_test.go
+++ b/pkg/cmd/pr/checkout/checkout_test.go
@@ -646,3 +646,45 @@ func TestPRCheckout_recurseSubmodules(t *testing.T) {
 	assert.Equal(t, "git submodule sync --recursive", strings.Join(ranCommands[3], " "))
 	assert.Equal(t, "git submodule update --init --recursive", strings.Join(ranCommands[4], " "))
 }
+
+func TestPRCheckout_force(t *testing.T) {
+	http := &httpmock.Registry{}
+
+	http.Register(httpmock.GraphQL(`query PullRequestByNumber\b`), httpmock.StringResponse(`
+	{ "data": { "repository": { "pullRequest": {
+		"number": 123,
+		"headRefName": "feature",
+		"headRepositoryOwner": {
+			"login": "hubot"
+		},
+		"headRepository": {
+			"name": "REPO"
+		},
+		"isCrossRepository": false,
+		"maintainerCanModify": false
+	} } } }
+	`))
+
+	ranCommands := [][]string{}
+	//nolint:staticcheck // SA1019 TODO: rewrite to use run.Stub
+	restoreCmd := run.SetPrepareCmd(func(cmd *exec.Cmd) run.Runnable {
+		switch strings.Join(cmd.Args, " ") {
+		case "git show-ref --verify -- refs/heads/feature":
+			return &test.OutputStub{}
+		default:
+			ranCommands = append(ranCommands, cmd.Args)
+			return &test.OutputStub{}
+		}
+	})
+	defer restoreCmd()
+
+	output, err := runCommand(http, nil, "master", `123 --force`)
+
+	assert.NoError(t, err)
+	assert.Equal(t, "", output.String())
+
+	assert.Equal(t, len(ranCommands), 3)
+	assert.Equal(t, "git fetch origin +refs/heads/feature:refs/remotes/origin/feature", strings.Join(ranCommands[0], " "))
+	assert.Equal(t, "git checkout feature", strings.Join(ranCommands[1], " "))
+	assert.Equal(t, "git reset --hard refs/remotes/origin/feature", strings.Join(ranCommands[2], " "))
+}