Add CapabilityCheck helper function

Signed-off-by: Javi Fontan <[email protected]>

Author: jfontan

fs.go

@@ -182,3 +182,10 @@ func Capabilities(fs Basic) Capability {
 
 	return capable.Capabilities()
 }
+
+// CapabilityCheck tests the filesystem for the provided capabilities and
+// returns true in case it supports all of them.
+func CapabilityCheck(fs Basic, capabilities Capability) bool {
+	fsCaps := Capabilities(fs)
+	return fsCaps&capabilities == capabilities
+}

fs_test.go

@@ -0,0 +1,37 @@
+package billy_test
+
+import (
+	"testing"
+
+	. "gopkg.in/src-d/go-billy.v4"
+	"gopkg.in/src-d/go-billy.v4/memfs"
+
+	. "gopkg.in/check.v1"
+)
+
+type FSSuite struct{}
+
+func Test(t *testing.T) { TestingT(t) }
+
+var _ = Suite(&FSSuite{})
+
+func (s *FSSuite) TestCapabilities(c *C) {
+	cases := []struct {
+		caps     Capability
+		expected bool
+	}{
+		{CapLock, false},
+		{CapRead, true},
+		{CapRead | CapWrite, true},
+		{CapRead | CapWrite | CapReadAndWrite | CapTruncate, true},
+		{CapRead | CapWrite | CapReadAndWrite | CapTruncate | CapLock, false},
+		{CapTruncate | CapLock, false},
+	}
+
+	// This filesystem supports all capabilities except for CapLock
+	mem := memfs.New()
+
+	for _, e := range cases {
+		c.Assert(CapabilityCheck(mem, e.caps), Equals, e.expected)
+	}
+}