Replace hardcoded gemfile path with methods to discover Gemfile for bundle binstub

lib/bundler/templates/Executable.bundler

@@ -38,10 +38,39 @@ m = Module.new do
   end
 
   def gemfile
-    gemfile = ENV["BUNDLE_GEMFILE"]
-    return gemfile if gemfile && !gemfile.empty?
+    gemfile = find_gemfile
+    return unless gemfile
+    File.expand_path(gemfile)
+  end
+
+  def find_gemfile
+    given = ENV["BUNDLE_GEMFILE"]
+    return given if given && !given.empty?
+    find_file(*gemfile_names)
+  end
 
-    File.expand_path("../<%= relative_gemfile_path %>", __FILE__)
+  def gemfile_names
+    ["Gemfile", "gems.rb"]
+  end
+
+  def find_file(*names)
+    search_up(*names) do |filename|
+      return filename if File.file?(filename)
+    end
+  end
+
+  def search_up(*names)
+    previous = nil
+    current  = File.expand_path(Dir.pwd)
+
+    until !File.directory?(current) || current == previous
+      names.each do |name|
+        filename = File.join(current, name)
+        yield filename
+      end
+      previous = current
+      current = File.expand_path("..", current)
+    end
   end
 
   def lockfile

spec/commands/binstubs_spec.rb

@@ -187,6 +187,67 @@
           end
         end
       end
+
+      context "when working with multiple gemfiles" do
+        let(:bundle_binstub) { bundled_app("bin/bundle") }
+        let(:load_bundle_exe) { "load Gem.bin_path(\"bundler\", \"bundle\")" }
+        let(:output_bundle_gemfile) { "puts ENV[\"BUNDLE_GEMFILE\"]" }
+
+        before do
+          build_repo2 do
+            build_gem "print_hello", "1.0" do |s|
+              s.executables = "print_hello"
+              s.bindir = "exe"
+              s.write "exe/print_hello", <<-R
+                puts "Hello!"
+              R
+            end
+            build_gem "print_goodbye", "1.0" do |s|
+              s.executables = "print_goodbye"
+              s.bindir = "exe"
+              s.write "exe/print_goodbye", <<-R
+                puts "Goodbye."
+              R
+            end
+          end
+
+          bundle! "config --global path #{bundled_app}"
+          bundle! "config --global bin #{bundled_app("bin")}"
+
+          install_gemfile! <<-G
+            source "file://#{gem_repo2}"
+          G
+          bundle! "binstubs bundler"
+        end
+
+        it "uses the correct Gemfile" do
+          create_file "one/Gemfile", <<-G
+            source "file://#{gem_repo2}"
+            gem "print_hello"
+          G
+          create_file "two/Gemfile", <<-G
+            source "file://#{gem_repo2}"
+            gem "print_goodbye"
+          G
+          Dir.chdir("one") { bundle! "install" }
+          Dir.chdir("two") { bundle! "install" }
+
+          binstub = File.read(bundled_app("bin/bundle"))
+          # Replace load statement with BUNDLE_GEMFILE puts
+          binstub.gsub!(load_bundle_exe, output_bundle_gemfile)
+          File.open(bundle_binstub, "w") {|f| f.puts binstub }
+
+          Dir.chdir("one") do
+            sys_exec "#{bundled_app("bin/bundle")} exec print_hello"
+            expect(out).to eq(bundled_app("one/Gemfile").to_s)
+          end
+
+          Dir.chdir("two") do
+            sys_exec "#{bundled_app("bin/bundle")} exec print_goodbye"
+            expect(out).to eq(bundled_app("two/Gemfile").to_s)
+          end
+        end
+      end
     end
 
     it "installs binstubs from git gems" do