Add more thorough tests for updates

shared/version.go

@@ -0,0 +1,57 @@
+package shared
+
+import (
+	"fmt"
+	"regexp"
+	"strconv"
+)
+
+type ParsedVersion struct {
+	MajorVersion int
+	MinorVersion int
+}
+
+func (pv ParsedVersion) GreaterThan(other ParsedVersion) bool {
+	if pv.MajorVersion == other.MajorVersion && pv.MinorVersion == other.MinorVersion {
+		return false
+	}
+	return !pv.LessThan(other)
+}
+
+func (pv ParsedVersion) LessThan(other ParsedVersion) bool {
+	if pv.MajorVersion != other.MajorVersion {
+		return pv.MajorVersion < other.MajorVersion
+	}
+	return pv.MinorVersion < other.MinorVersion
+}
+
+func (pv ParsedVersion) Decrement() ParsedVersion {
+	if pv.MinorVersion > 1 {
+		return ParsedVersion{pv.MajorVersion, pv.MinorVersion - 1}
+	}
+	panic("cannot decrement() when MinorVersion == 0")
+}
+
+func (pv ParsedVersion) String() string {
+	return fmt.Sprintf("v%d.%d", pv.MajorVersion, pv.MinorVersion)
+}
+
+func ParseVersionString(versionString string) (ParsedVersion, error) {
+	re := regexp.MustCompile(`v(\d+)[.](\d+)`)
+	matches := re.FindAllStringSubmatch(versionString, -1)
+	if len(matches) != 1 {
+		return ParsedVersion{}, fmt.Errorf("failed to parse version=%#v (matches=%#v)", versionString, matches)
+	}
+	if len(matches[0]) != 3 {
+		return ParsedVersion{}, fmt.Errorf("failed to parse version=%#v (matches[0]=%#v)", versionString, matches[0])
+	}
+	MajorVersion, err := strconv.Atoi(matches[0][1])
+	if err != nil {
+		return ParsedVersion{}, fmt.Errorf("failed to parse major version %#v", matches[0][1])
+	}
+	MinorVersion, err := strconv.Atoi(matches[0][2])
+	if err != nil {
+		return ParsedVersion{}, fmt.Errorf("failed to parse minor version %#v", matches[0][2])
+	}
+	return ParsedVersion{MajorVersion, MinorVersion}, nil
+}