Make sure git gems are properly cached

When using the `cache_all` setting, git gems are also cached. Also, when
using `--all-platforms`, gems for all platforms should be cached. Since
`git` gems supporting multiple platforms usually provide a single
gemspec, we need to special case that, otherwise the versions of the git
gems for platforms different than the running one wouldn't be found
because the gemspec would've been evaluated only for the current
platform.

bundler/lib/bundler/lazy_specification.rb

@@ -79,7 +79,11 @@ def __materialize__
       @specification = if source.is_a?(Source::Gemspec) && source.gemspec.name == name
         source.gemspec.tap {|s| s.source = source }
       else
-        search_object = Bundler.feature_flag.specific_platform? || Bundler.settings[:force_ruby_platform] ? self : Dependency.new(name, version)
+        search_object = if source.is_a?(Source::Path)
+          Dependency.new(name, version)
+        else
+          Bundler.feature_flag.specific_platform? || Bundler.settings[:force_ruby_platform] ? self : Dependency.new(name, version)
+        end
         platform_object = Gem::Platform.new(platform)
         candidates = source.specs.search(search_object)
         same_platform_candidates = candidates.select do |spec|

bundler/spec/install/gemfile/specific_platform_spec.rb

@@ -33,6 +33,41 @@
         to all(exist)
     end
 
+    it "caches multiplatform git gems with a single gemspec when --all-platforms is passed" do
+      git = build_git "pg_array_parser", "1.0"
+
+      gemfile <<-G
+        gem "pg_array_parser", :git => "#{lib_path("pg_array_parser-1.0")}"
+      G
+
+      lockfile <<-L
+        GIT
+          remote: #{lib_path("pg_array_parser-1.0")}
+          revision: #{git.ref_for("master")}
+          specs:
+            pg_array_parser (1.0-java)
+            pg_array_parser (1.0)
+
+        GEM
+          specs:
+
+        PLATFORMS
+          java
+          #{lockfile_platforms}
+
+        DEPENDENCIES
+          pg_array_parser!
+
+        BUNDLED WITH
+           #{Bundler::VERSION}
+      L
+
+      bundle "config set --local cache_all true"
+      bundle "cache --all-platforms"
+
+      expect(err).to be_empty
+    end
+
     it "uses the platform-specific gem with extra dependencies" do
       setup_multiplatform_gem_with_different_dependencies_per_platform
       install_gemfile <<-G