[SourcesManager] Ensure the master repo is shallow cloned

Closes https://github.com/CocoaPods/CocoaPods/issues/2586.

CHANGELOG.md

@@ -44,6 +44,11 @@ To install or update CocoaPods see this [guide](http://docs.cocoapods.org/guides
   [Samuel Giddins](https://github.com/segiddins)
   [#2553](https://github.com/CocoaPods/CocoaPods/issues/2553)
 
+* Ensures that the master repo is shallow cloned when added via a Podfile
+  `source` directive.  
+  [Samuel Giddins](https://github.com/segiddins)
+  [#3586](https://github.com/CocoaPods/CocoaPods/issues/2586)
+
 
 ## 0.34.1
 

lib/cocoapods/sources_manager.rb

@@ -40,7 +40,9 @@ module Pod
           previous_title_level = UI.title_level
           UI.title_level = 0
           begin
-            Command::Repo::Add.new(CLAide::ARGV.new([name, url])).run
+            argv = [name, url]
+            argv << '--shallow' if name =~ /^master(-\d+)?$/
+            Command::Repo::Add.new(CLAide::ARGV.new(argv)).run
           rescue Informative => e
             raise Informative, "Unable to add a source with url `#{url}` " \
               "named `#{name}`.\nYou can try adding it manually in " \