Fix oci.hasPrefix to operate correctly on Windows

Due to use of filepath.Clean(), on Windows we end up operating on the
paths in Windows-slashed form, even if the inputs were Unix-slashed.

Signed-off-by: Paul "TBBle" Hampson <Paul.Hampson@Pobox.com>

executor/oci/mounts.go

@@ -76,11 +76,11 @@ func withROBind(src, dest string) func(m []specs.Mount) ([]specs.Mount, error) {
 
 func hasPrefix(p, prefixDir string) bool {
 	prefixDir = filepath.Clean(prefixDir)
-	if prefixDir == "/" {
+	if filepath.Base(prefixDir) == string(filepath.Separator) {
 		return true
 	}
 	p = filepath.Clean(p)
-	return p == prefixDir || strings.HasPrefix(p, prefixDir+"/")
+	return p == prefixDir || strings.HasPrefix(p, prefixDir+string(filepath.Separator))
 }
 
 func removeMountsWithPrefix(mounts []specs.Mount, prefixDir string) []specs.Mount {

executor/oci/mounts_test.go

@@ -1,6 +1,7 @@
 package oci
 
 import (
+	"runtime"
 	"testing"
 
 	"github.com/stretchr/testify/assert"
@@ -49,6 +50,45 @@ func TestHasPrefix(t *testing.T) {
 			expected: false,
 		},
 	}
+	if runtime.GOOS == "windows" {
+		testCases = append(testCases,
+			testCase{
+				path:     "C:\\foo\\bar",
+				prefix:   "C:\\foo",
+				expected: true,
+			},
+			testCase{
+				path:     "C:\\foo\\bar",
+				prefix:   "C:\\foo\\",
+				expected: true,
+			},
+			testCase{
+				path:     "C:\\foo\\bar",
+				prefix:   "C:\\",
+				expected: true,
+			},
+			testCase{
+				path:     "C:\\foo",
+				prefix:   "C:\\foo",
+				expected: true,
+			},
+			testCase{
+				path:     "C:\\foo\\bar",
+				prefix:   "C:\\bar",
+				expected: false,
+			},
+			testCase{
+				path:     "C:\\foo\\bar",
+				prefix:   "foo",
+				expected: false,
+			},
+			testCase{
+				path:     "C:\\foobar",
+				prefix:   "C:\\foo",
+				expected: false,
+			},
+		)
+	}
 	for i, tc := range testCases {
 		actual := hasPrefix(tc.path, tc.prefix)
 		assert.Equal(t, tc.expected, actual, "#%d: under(%q,%q)", i, tc.path, tc.prefix)