Initial 'v' in versions should not be compared on (fixes #980)

internal/upgrade/upgrade_common.go

@@ -153,6 +153,10 @@ func CompareVersions(a, b string) int {
 // Split a version into parts.
 // "1.2.3-beta.2" -> []int{1, 2, 3}, []interface{}{"beta", 2}
 func versionParts(v string) ([]int, []interface{}) {
+	if strings.HasPrefix(v, "v") || strings.HasPrefix(v, "V") {
+		// Strip initial 'v' or 'V' prefix if present.
+		v = v[1:]
+	}
 	parts := strings.SplitN(v, "+", 2)
 	parts = strings.SplitN(parts[0], "-", 2)
 	fields := strings.Split(parts[0], ".")

internal/upgrade/upgrade_test.go

@@ -42,6 +42,10 @@ var testcases = []struct {
 	{"1.0.0+45", "1.0.0+23-dev-foo", 0},
 	{"1.0.0-beta.23+45", "1.0.0-beta.23+23-dev-foo", 0},
 	{"1.0.0-beta.3+99", "1.0.0-beta.24+0", -1},
+
+	{"v1.1.2", "1.1.2", 0},
+	{"v1.1.2", "V1.1.2", 0},
+	{"1.1.2", "V1.1.2", 0},
 }
 
 func TestCompareVersions(t *testing.T) {