[Repo::Push] Allow disabling overwriting published specs

CHANGELOG.md

@@ -16,6 +16,10 @@ To install release candidates run `[sudo] gem install cocoapods --pre`
   [Keith Smiley](https://github.com/keith)
   [#7346](https://github.com/CocoaPods/CocoaPods/pull/7346)
 
+* Add a `--no-overwrite` flag to `pod repo push` to disable overwriting
+  existing specs that have already been pushed.  
+  [Samuel Giddins](https://github.com/segiddins)
+
 ##### Bug Fixes
 
 * Do not attempt compilation for pods with no sources and skipping import validation  

lib/cocoapods/command/repo/push.rb

@@ -36,6 +36,7 @@ module Pod
             ['--use-json', 'Push JSON spec to repo'],
             ['--swift-version=VERSION', 'The SWIFT_VERSION that should be used when linting the spec. ' \
              'This takes precedence over a .swift-version file.'],
+            ['--no-overwrite', 'Disallow pushing that would overwrite an existing spec.'],
           ].concat(super)
         end
 
@@ -54,6 +55,7 @@ module Pod
           @swift_version = argv.option('swift-version', nil)
           @skip_import_validation = argv.flag?('skip-import-validation', false)
           @skip_tests = argv.flag?('skip-tests', false)
+          @allow_overwrite = argv.flag?('overwrite', true)
           super
         end
 
@@ -183,6 +185,9 @@ module Pod
             if @message && !@message.empty?
               message = @message
             elsif output_path.exist?
+              unless @allow_overwrite
+                raise Informative, "#{spec} already exists and overwriting has been disabled."
+              end
               message = "[Fix] #{spec}"
             elsif output_path.dirname.directory?
               message = "[Update] #{spec}"

spec/functional/command/repo/push_spec.rb

@@ -108,6 +108,20 @@ module Pod
       (@upstream + 'PushTest/1.4/PushTest.podspec').should.not.exist?
     end
 
+    it 'refuses to push if --no-overwrite is passed and the spec exists' do
+      cmd = command('repo', 'push', 'master', 'JSONKit.podspec', '--no-overwrite')
+      Dir.chdir(@upstream) { `git checkout -b tmp_for_push -q` }
+      cmd.expects(:validate_podspec_files).returns(true)
+
+      e = lambda { Dir.chdir(temporary_directory) { cmd.run } }.should.raise Pod::Informative
+      e.message.should == '[!] JSONKit (1.4) already exists and overwriting has been disabled.'
+
+      cmd = command('repo', 'push', 'master', 'PushTest.podspec', '--no-overwrite')
+      cmd.expects(:validate_podspec_files).returns(true)
+      Dir.chdir(temporary_directory) { cmd.run }
+      Pod::UI.output.should.include('[Add] PushTest (1.4)')
+    end
+
     it 'generate a message for commit' do
       cmd = command('repo', 'push', 'master')
       Dir.chdir(@upstream) { `git checkout -b tmp_for_push -q` }