From b44660ac3da2f8e651372c40ae803782bddea283 Mon Sep 17 00:00:00 2001
From: Robert Liebowitz <rliebz@gmail.com>
Date: Sat, 28 Oct 2017 03:00:11 -0400
Subject: [PATCH] Consider case when sorting strings

This makes sorting flags and other sections consistent with how most
command line tools function, by placing both flags `-A` and `-a` before
a flag `-B`.
---
 category.go  |  2 +-
 command.go   |  2 +-
 flag.go      |  2 +-
 sort.go      | 29 +++++++++++++++++++++++++++++
 sort_test.go | 30 ++++++++++++++++++++++++++++++
 5 files changed, 62 insertions(+), 3 deletions(-)
 create mode 100644 sort.go
 create mode 100644 sort_test.go

diff --git a/category.go b/category.go
index 1a60550..bf3c73c 100644
--- a/category.go
+++ b/category.go
@@ -10,7 +10,7 @@ type CommandCategory struct {
 }
 
 func (c CommandCategories) Less(i, j int) bool {
-	return c[i].Name < c[j].Name
+	return lexicographicLess(c[i].Name, c[j].Name)
 }
 
 func (c CommandCategories) Len() int {
diff --git a/command.go b/command.go
index 502fc9f..be8f8f0 100644
--- a/command.go
+++ b/command.go
@@ -73,7 +73,7 @@ func (c CommandsByName) Len() int {
 }
 
 func (c CommandsByName) Less(i, j int) bool {
-	return c[i].Name < c[j].Name
+	return lexicographicLess(c[i].Name, c[j].Name)
 }
 
 func (c CommandsByName) Swap(i, j int) {
diff --git a/flag.go b/flag.go
index b17f5b9..53fb8bb 100644
--- a/flag.go
+++ b/flag.go
@@ -53,7 +53,7 @@ func (f FlagsByName) Len() int {
 }
 
 func (f FlagsByName) Less(i, j int) bool {
-	return f[i].GetName() < f[j].GetName()
+	return lexicographicLess(f[i].GetName(), f[j].GetName())
 }
 
 func (f FlagsByName) Swap(i, j int) {
diff --git a/sort.go b/sort.go
new file mode 100644
index 0000000..23d1c2f
--- /dev/null
+++ b/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
+}
diff --git a/sort_test.go b/sort_test.go
new file mode 100644
index 0000000..662ef9b
--- /dev/null
+++ b/sort_test.go
@@ -0,0 +1,30 @@
+package cli
+
+import "testing"
+
+var lexicographicLessTests = []struct {
+	i        string
+	j        string
+	expected bool
+}{
+	{"", "a", true},
+	{"a", "", false},
+	{"a", "a", false},
+	{"a", "A", false},
+	{"A", "a", true},
+	{"aa", "a", false},
+	{"a", "aa", true},
+	{"a", "b", true},
+	{"a", "B", true},
+	{"A", "b", true},
+	{"A", "B", true},
+}
+
+func TestLexicographicLess(t *testing.T) {
+	for _, test := range lexicographicLessTests {
+		actual := lexicographicLess(test.i, test.j)
+		if test.expected != actual {
+			t.Errorf(`expected string "%s" to come before "%s"`, test.i, test.j)
+		}
+	}
+}