accepts 0B, -1B, 0T, etc for flags for non push commands

Signed-off-by: Matthew Kocher <mkocher@vmware.com>

command/flag/bytes_with_unlimited.go

@@ -1,6 +1,7 @@
 package flag
 
 import (
+	"regexp"
 	"strings"
 
 	"code.cloudfoundry.org/bytefmt"
@@ -10,17 +11,26 @@ import (
 
 type BytesWithUnlimited types.NullInt
 
+var zeroBytes *regexp.Regexp = regexp.MustCompile(`^0[KMGT]?B?$`)
+var negativeOneBytes *regexp.Regexp = regexp.MustCompile(`^-1[KMGT]?B?$`)
+
 func (m *BytesWithUnlimited) UnmarshalFlag(val string) error {
 	if val == "" {
 		return nil
 	}
 
-	if val == "-1" {
+	if negativeOneBytes.MatchString(val) {
 		m.Value = -1
 		m.IsSet = true
 		return nil
 	}
 
+	if zeroBytes.MatchString(val) {
+		m.Value = 0
+		m.IsSet = true
+		return nil
+	}
+
 	size, err := ConvertToBytes(val)
 	if err != nil {
 		return err

command/flag/bytes_with_unlimited_test.go

@@ -77,6 +77,26 @@ var _ = Describe("BytesWithUnlimited", func() {
 				Expect(err).ToNot(HaveOccurred())
 				Expect(bytesWithUnlimited.Value).To(BeEquivalentTo(-1))
 			})
+
+			It("accepts units", func() {
+				err := bytesWithUnlimited.UnmarshalFlag("-1T")
+				Expect(err).ToNot(HaveOccurred())
+				Expect(bytesWithUnlimited.Value).To(BeEquivalentTo(-1))
+			})
+		})
+
+		When("the value is 0", func() {
+			It("set's the value to 0", func() {
+				err := bytesWithUnlimited.UnmarshalFlag("0")
+				Expect(err).ToNot(HaveOccurred())
+				Expect(bytesWithUnlimited.Value).To(BeEquivalentTo(0))
+			})
+
+			It("accepts units", func() {
+				err := bytesWithUnlimited.UnmarshalFlag("0TB")
+				Expect(err).ToNot(HaveOccurred())
+				Expect(bytesWithUnlimited.Value).To(BeEquivalentTo(0))
+			})
 		})
 
 		When("the suffix is lowercase", func() {