tests: split testParentDir by UID

When we run tests as root, they will leave root-owned files
in testParentDir, which causes trouble when we run tests as
a normal user later on. Split by UID.

internal/syscallcompat/main_test.go

@@ -16,7 +16,8 @@ func TestMain(m *testing.M) {
 		fmt.Println(err)
 		os.Exit(1)
 	}
-	parent := "/tmp/gocryptfs-test-parent"
+	// Cannot import test_helpers because of import cycle
+	parent := fmt.Sprintf("/tmp/gocryptfs-test-parent-%d", os.Getuid())
 	err = os.MkdirAll(parent, 0700)
 	if err != nil {
 		fmt.Println(err)

test.bash

@@ -10,7 +10,7 @@ set -eu
 
 cd "$(dirname "$0")"
 MYNAME=$(basename "$0")
-TESTDIR=$TMPDIR/gocryptfs-test-parent
+TESTDIR=$TMPDIR/gocryptfs-test-parent-$UID
 mkdir -p $TESTDIR
 LOCKFILE=$TESTDIR/$MYNAME.lock
 

tests/test_helpers/helpers.go

@@ -59,8 +59,8 @@ func init() {
 func doInit() {
 	X255 = string(bytes.Repeat([]byte("X"), 255))
 	MountInfo = make(map[string]mountInfo)
-
-	testParentDir := os.TempDir() + "/gocryptfs-test-parent"
+	// Something like /tmp/gocryptfs-test-parent-1234
+	testParentDir := fmt.Sprintf("%s/gocryptfs-test-parent-%d", os.TempDir(), os.Getuid())
 	os.MkdirAll(testParentDir, 0700)
 	var err error
 	TmpDir, err = ioutil.TempDir(testParentDir, "")