Update CocoaPods for alpha13. (#835)

* Update CocoaPods for alpha13.

* Use '>=' and '<' for version descriptors instead.

CGRPCZlib.podspec

@@ -2,7 +2,7 @@ Pod::Spec.new do |s|
 
     s.name = 'CGRPCZlib'
     s.module_name = 'CGRPCZlib'
-    s.version = '1.0.0-alpha.12'
+    s.version = '1.0.0-alpha.13'
     s.license = { :type => 'Apache 2.0', :file => 'LICENSE' }
     s.summary = 'Compression library that provides in-memory compression and decompression functions'
     s.homepage = 'https://www.grpc.io'

gRPC-Swift.podspec

@@ -16,12 +16,12 @@ Pod::Spec.new do |s|
     s.tvos.deployment_target = '10.0'
     s.source_files = 'Sources/GRPC/**/*.{swift,c,h}'
 
-    s.dependency 'Logging', '1.2.0'
-    s.dependency 'SwiftNIO', '2.18.0'
-    s.dependency 'SwiftNIOHTTP2', '1.12.1'
-    s.dependency 'SwiftNIOSSL', '2.7.4'
-    s.dependency 'SwiftNIOTransportServices', '1.6.0'
-    s.dependency 'SwiftProtobuf', '1.9.0'
+    s.dependency 'Logging', '>= 1.2.0', '< 2'
+    s.dependency 'SwiftNIO', '>= 2.18.0', '< 3'
+    s.dependency 'SwiftNIOHTTP2', '>= 1.12.1', '< 2'
+    s.dependency 'SwiftNIOSSL', '>= 2.7.4', '< 3'
+    s.dependency 'SwiftNIOTransportServices', '>= 1.6.0', '< 2'
+    s.dependency 'SwiftProtobuf', '>= 1.9.0', '< 2'
     s.dependency 'CGRPCZlib', s.version.to_s
 
 end

scripts/build_podspecs.py

@@ -118,7 +118,7 @@ class PodManager:
     def publish(self, pod_name):
         os.system('pod repo update')
         print('    Publishing %s.podspec' % (pod_name))
-        os.system('pod trunk push %s/%s.podspec' % (self.directory, pod_name))
+        os.system('pod trunk push --synchronous %s/%s.podspec' % (self.directory, pod_name))
 
     def build_pods(self):
         cgrpczlib_pod = Pod(
@@ -172,8 +172,9 @@ def get_grpc_deps():
     for obj in data['object']['pins']:
         package = process_package(obj['package'])
         version = obj['state']['version']
+        next_major_version = int(version.split('.')[0]) + 1
 
-        deps.append(Dependency(package, version, False))
+        deps.append(Dependency(package, '\'>= {}\', \'< {}\''.format(version, next_major_version)))
 
     return deps