write temporary test files in temp directory (spf13#937)

Instead of writing to the current working directory, pick a random temp
directory to test the CLI commands, keeping the working directory free
of test side effects.

In some cases the system default temp dir will also have some advantages
like being mounted in an in-memory tmpfs.

cobra/cmd/init_test.go

@@ -11,9 +11,8 @@ import (
 )
 
 func getProject() *Project {
-	wd, _ := os.Getwd()
 	return &Project{
-		AbsolutePath: fmt.Sprintf("%s/testproject", wd),
+		AbsolutePath: fmt.Sprintf("%s/testproject", mustTempDir()),
 		Legal:        getLicense(),
 		Copyright:    copyrightLine(),
 		AppName:      "testproject",
@@ -22,6 +21,14 @@ func getProject() *Project {
 	}
 }
 
+func mustTempDir() string {
+	dir, err := ioutil.TempDir("", "cobra_cli_test_")
+	if err != nil {
+		panic(err)
+	}
+	return dir
+}
+
 func TestGoldenInitCmd(t *testing.T) {
 
 	dir, err := ioutil.TempDir("", "cobra-init")