Fix mock generation

* Switch to fork that supports generating mocks for vendored dependencies (golang/mock#28)
* Install vendored mockgen before generating mocks
* Do not try to find files when no directories are found

.gitmodules

@@ -3,7 +3,7 @@
 	url = https://github.com/cloudfoundry/cli.git
 [submodule "vendor/github.com/golang/mock"]
 	path = vendor/github.com/golang/mock
-	url = https://github.com/golang/mock.git
+	url = https://github.com/pcfdev-forks/mock.git
 [submodule "vendor/github.com/onsi/ginkgo"]
 	path = vendor/github.com/onsi/ginkgo
 	url = https://github.com/onsi/ginkgo

bin/generate-mocks

@@ -2,6 +2,9 @@
 
 pcfdev_dir=$(cd `dirname $0` && cd .. && pwd)
 mocks_dirs=$(go list -f '{{.Dir}}' github.com/pivotal-cf/pcfdev-cli/... | grep -v /vendor/ | grep '/mocks$')
-find $mocks_dirs -name "*.go" -exec rm {} \;
+if [[ -n "$mocks_dirs" ]]; then
+  find $mocks_dirs -name "*.go" -exec rm {} \;
+fi
 
+go install github.com/pivotal-cf/pcfdev-cli/vendor/github.com/golang/mock/mockgen
 go generate $(go list github.com/pivotal-cf/pcfdev-cli/... | grep -v /vendor/)