fix: checkout existing branch

3 files changed, 31 insertions, 19 deletions

diff --git a/lib/dependabot/git.rb b/lib/dependabot/git.rb
index 26869ed..7b6598c 100644
--- a/lib/dependabot/git.rb
+++ b/lib/dependabot/git.rb
@@ -13,7 +13,7 @@ module Dependabot
     end
 
     def checkout(branch:)
-      repo.create_branch(branch, repo.head.name)
+      repo.create_branch(branch, repo.head.name) unless repo.branches[branch]
       repo.checkout(branch)
     end
 
diff --git a/spec/integration/dependabot/git_spec.rb b/spec/integration/dependabot/git_spec.rb
index 9dfabcb..8dea207 100644
--- a/spec/integration/dependabot/git_spec.rb
+++ b/spec/integration/dependabot/git_spec.rb
@@ -1,24 +1,25 @@
 # frozen_string_literal: true
 
 RSpec.describe ::Dependabot::Git do
-  def setup_git_repo(path)
-    system "git init --quiet #{path}"
-    system "git config user.email you@example.com"
-    system "git config user.name example"
-    system "echo 'hello' > README.md"
-    system "git add README.md"
-    system "git commit --quiet --no-gpg-sign -m 'initial commit'"
-    system "echo 'change' > README.md"
+  def within_git_repo
+    within_tmp_dir do |path|
+      system "git init --quiet #{path}"
+      system "git config user.email you@example.com"
+      system "git config user.name example"
+      system "echo 'hello' > README.md"
+      system "git add README.md"
+      system "git commit --quiet --no-gpg-sign -m 'initial commit'"
+      system "echo 'change' > README.md"
+      yield described_class.new(path)
+    end
   end
 
   describe "#checkout" do
     context "when the branch does not exist" do
-      let(:branch_name) { "example" }
+      let(:branch_name) { SecureRandom.uuid }
 
       it "creates a new branch" do
-        within_tmp_dir do |path|
-          setup_git_repo(path)
-          subject = described_class.new(path)
+        within_git_repo do |subject|
           subject.checkout(branch: branch_name)
 
           expect(`git branch`).to include(branch_name)
@@ -26,9 +27,21 @@ RSpec.describe ::Dependabot::Git do
       end
 
       it "switches to the new branch" do
-        within_tmp_dir do |path|
-          setup_git_repo(path)
-          subject = described_class.new(path)
+        within_git_repo do |subject|
+          subject.checkout(branch: branch_name)
+
+          expect(File.read(".git/HEAD").chomp).to eql("ref: refs/heads/#{branch_name}")
+        end
+      end
+    end
+
+    context "when the branch already exists" do
+      let(:branch_name) { SecureRandom.uuid }
+
+      it "switches to that branch" do
+        within_git_repo do |subject|
+          system "git branch #{branch_name}"
+
           subject.checkout(branch: branch_name)
 
           expect(File.read(".git/HEAD").chomp).to eql("ref: refs/heads/#{branch_name}")
@@ -40,9 +53,7 @@ RSpec.describe ::Dependabot::Git do
   describe "#commit" do
     context "when a tracked file is changed" do
       def within_dir
-        within_tmp_dir do |path|
-          setup_git_repo(path)
-          subject = described_class.new(path)
+        within_git_repo do |subject|
           subject.checkout(branch: "example")
           subject.commit(all: true, message: "The message")
           yield
diff --git a/spec/spec_helper.rb b/spec/spec_helper.rb
index 6524bfc..1cb59bd 100644
--- a/spec/spec_helper.rb
+++ b/spec/spec_helper.rb
@@ -3,6 +3,7 @@
 require "bundler/setup"
 require "dependabot/cli"
 require "securerandom"
+require "debug"
 require "tmpdir"
 require "webmock/rspec"