switched to go-mod, updated codegangsta/cli -> urfave/cli

vendor/github.com/urfave/cli/sort.go

@@ -0,0 +1,29 @@
+package cli
+
+import "unicode"
+
+// lexicographicLess compares strings alphabetically considering case.
+func lexicographicLess(i, j string) bool {
+	iRunes := []rune(i)
+	jRunes := []rune(j)
+
+	lenShared := len(iRunes)
+	if lenShared > len(jRunes) {
+		lenShared = len(jRunes)
+	}
+
+	for index := 0; index < lenShared; index++ {
+		ir := iRunes[index]
+		jr := jRunes[index]
+
+		if lir, ljr := unicode.ToLower(ir), unicode.ToLower(jr); lir != ljr {
+			return lir < ljr
+		}
+
+		if ir != jr {
+			return ir < jr
+		}
+	}
+
+	return i < j
+}