add version pkg

Docker-DCO-1.1-Signed-off-by: Victor Vieux <victor.vieux@docker.com> (github: vieux)

version/version.go

@@ -0,0 +1,52 @@
+package version
+
+import (
+	"strconv"
+	"strings"
+)
+
+type Version string
+
+func (me Version) compareTo(other string) int {
+	var (
+		meTab    = strings.Split(string(me), ".")
+		otherTab = strings.Split(other, ".")
+	)
+	for i, s := range meTab {
+		var meInt, otherInt int
+		meInt, _ = strconv.Atoi(s)
+		if len(otherTab) > i {
+			otherInt, _ = strconv.Atoi(otherTab[i])
+		}
+		if meInt > otherInt {
+			return 1
+		}
+		if otherInt > meInt {
+			return -1
+		}
+	}
+	if len(otherTab) > len(meTab) {
+		return -1
+	}
+	return 0
+}
+
+func (me Version) LessThan(other string) bool {
+	return me.compareTo(other) == -1
+}
+
+func (me Version) LessThanOrEqualTo(other string) bool {
+	return me.compareTo(other) <= 0
+}
+
+func (me Version) GreaterThan(other string) bool {
+	return me.compareTo(other) == 1
+}
+
+func (me Version) GreaterThanOrEqualTo(other string) bool {
+	return me.compareTo(other) >= 0
+}
+
+func (me Version) Equal(other string) bool {
+	return me.compareTo(other) == 0
+}