Make git_source work in nested groups

If you declare a `git_source` at the top level of your Gemfile or a spec in
Appraisals, it will substitute the gem source in `gem` declarations. If you
want to use those gem sources in nested groups declared with `group`,
`platforms`, `platform`, `source`, `git`, or `path`, the `git_source`
declarations from the top level aren't inherited, so they don't work like they
do with bundler.

Fortunately, in `BundlerDSL` there's a protected `git_sources` writer, and all
the groups are also declared in that file. It should be easy enough to assign
all of the group objects to a copy of the `git_sources`. That would make the
substitutions work.

Fixes #159.

lib/appraisal/bundler_dsl.rb

@@ -29,20 +29,23 @@ def gem(name, *requirements)
     end
 
     def group(*names, &block)
-      @groups[names] ||= Group.new(names)
+      @groups[names] ||=
+        Group.new(names).tap { |g| g.git_sources = @git_sources.dup }
       @groups[names].run(&block)
     end
 
     def platforms(*names, &block)
-      @platforms[names] ||= Platform.new(names)
+      @platforms[names] ||=
+        Platform.new(names).tap { |g| g.git_sources = @git_sources.dup }
       @platforms[names].run(&block)
     end
 
     alias_method :platform, :platforms
 
     def source(source, &block)
       if block_given?
-        @source_blocks[source] ||= Source.new(source)
+        @source_blocks[source] ||=
+          Source.new(source).tap { |g| g.git_sources = @git_sources.dup }
         @source_blocks[source].run(&block)
       else
         @sources << source
@@ -54,12 +57,14 @@ def ruby(ruby_version)
     end
 
     def git(source, options = {}, &block)
-      @gits[source] ||= Git.new(source, options)
+      @gits[source] ||=
+        Git.new(source, options).tap { |g| g.git_sources = @git_sources.dup }
       @gits[source].run(&block)
     end
 
     def path(source, options = {}, &block)
-      @paths[source] ||= Path.new(source, options)
+      @paths[source] ||=
+        Path.new(source, options).tap { |g| g.git_sources = @git_sources.dup }
       @paths[source].run(&block)
     end
 

spec/acceptance/appraisals_file_bundler_dsl_compatibility_spec.rb

@@ -3,7 +3,7 @@
 describe 'Appraisals file Bundler DSL compatibility' do
   it 'supports all Bundler DSL in Appraisals file' do
     build_gems %w(bagel orange_juice milk waffle coffee ham sausage pancake)
-    build_git_gems %w(egg croissant pain_au_chocolat)
+    build_git_gems %w(egg croissant pain_au_chocolat omelette)
 
     build_gemfile <<-Gemfile
       source 'https://rubygems.org'
@@ -23,6 +23,7 @@
 
       group :breakfast do
         gem 'orange_juice'
+        gem "omelette", :custom_git_source => "omelette"
       end
 
       platforms :ruby, :jruby do
@@ -106,6 +107,7 @@
 
       group :breakfast do
         gem "orange_juice"
+        gem "omelette", :git => "../../gems/omelette"
         gem "bacon"
 
         platforms :rbx do