[Git] update regex match for branch commit

CHANGELOG.md

@@ -8,7 +8,9 @@
 
 ##### Bug Fixes
 
-* None.  
+* Improves handling of multiple results from `git ls-remote` by using branch name in commit regex match.  
+  [Sean Reinhardt](https://github.com/seanreinhardtapps)
+  [#88](https://github.com/CocoaPods/cocoapods-downloader/issues/88)
 
 
 ## 1.3.0 (2019-11-14)

lib/cocoapods-downloader/git.rb

@@ -27,16 +27,35 @@ def self.preprocess_options(options)
                    options[:git],
                    options[:branch]]
         output = Git.execute_command('git', command)
-        match = /^([a-z0-9]*)\t.*/.match(output)
+        match = commit_from_ls_remote output, options[:branch]
 
         return options if match.nil?
 
-        options[:commit] = match[1]
+        options[:commit] = match
         options.delete(:branch)
 
         options
       end
 
+      # Matches a commit from the brances reported by git ls-remote.
+      #
+      # @note   When there is a branch and tag with the same name, it will match
+      #         the branch, since `refs/heads` is sorted before `refs/tags`.
+      #
+      # @param  [String] output
+      #         The output from git ls-remote.
+      #
+      # @param  [String] branch_name
+      #         The desired branch to match a commit to.
+      #
+      def self.commit_from_ls_remote(output, branch_name)
+        return nil if branch_name.nil?
+        match = %r{([a-z0-9]*)\trefs\/(heads|tags)\/#{Regexp.quote(branch_name)}}.match(output)
+        match[1] unless match.nil?
+      end
+
+      private_class_method :commit_from_ls_remote
+
       private
 
       # @!group Base class hooks

spec/git_spec.rb

@@ -217,6 +217,53 @@ def ensure_only_one_ref(folder)
         end
       end
 
+      describe ':commit_from_ls_remote' do
+        it 'finds commit for a branch' do
+          test_commit = 'abcde'
+          test_branch = 'stable'
+          test_output = "#{test_commit}\trefs/heads/#{test_branch}"
+          result = Git.send(:commit_from_ls_remote, test_output, test_branch)
+          result.should == test_commit
+        end
+        it 'returns nil for no match' do
+          test_commit = 'abcde'
+          test_branch = 'stable'
+          test_output = "#{test_commit}\trefs/heads/other_branch"
+          result = Git.send(:commit_from_ls_remote, test_output, test_branch)
+          result.should.nil?
+        end
+        it 'can match a commit for a tag' do
+          test_commit = '12345'
+          test_branch = 'stable'
+          test_output = "#{test_commit}\trefs/tags/#{test_branch}"
+          result = Git.send(:commit_from_ls_remote, test_output, test_branch)
+          result.should == test_commit
+        end
+        it 'finds correct commit from multiple ls-remote branches' do
+          test_commit1 = 'abcde'
+          test_branch1 = 'stable'
+          test_commit2 = '12345'
+          test_branch2 = 'release/stable'
+          test_output = "#{test_commit1}\trefs/heads/#{test_branch1}\n#{test_commit2}\trefs/heads/#{test_branch2}"
+          result1 = Git.send(:commit_from_ls_remote, test_output, test_branch1)
+          result1.should == test_commit1
+          result2 = Git.send(:commit_from_ls_remote, test_output, test_branch2)
+          result2.should == test_commit2
+        end
+        it 'returns a branch over a tag' do
+          test_commit1 = 'abcde'
+          test_branch = 'stable'
+          test_commit2 = '12345'
+          test_output = "#{test_commit1}\trefs/heads/#{test_branch}\n#{test_commit2}\trefs/tags/#{test_branch}"
+          result = Git.send(:commit_from_ls_remote, test_output, test_branch)
+          result.should == test_commit1
+        end
+        it 'handles nil inputs' do
+          Git.send(:commit_from_ls_remote, nil, 'test_branch').should.nil?
+          Git.send(:commit_from_ls_remote, "123\trefs/heads/abc", nil).should.nil?
+        end
+      end
+
       describe '::preprocess_options' do
         it 'skips non-branch requests' do
           options = { :git => fixture_url('git-repo'), :commit => 'aaaa' }