More expansions in template repositories (#10021)

* Super expansion
* Explain which features are in 1.11 vs 1.12
* Move imports

Signed-off-by: jolheiser <john.olheiser@gmail.com>

vendor/github.com/huandu/xstrings/format.go

@@ -0,0 +1,170 @@
+// Copyright 2015 Huan Du. All rights reserved.
+// Licensed under the MIT license that can be found in the LICENSE file.
+
+package xstrings
+
+import (
+	"bytes"
+	"unicode/utf8"
+)
+
+// ExpandTabs can expand tabs ('\t') rune in str to one or more spaces dpending on
+// current column and tabSize.
+// The column number is reset to zero after each newline ('\n') occurring in the str.
+//
+// ExpandTabs uses RuneWidth to decide rune's width.
+// For example, CJK characters will be treated as two characters.
+//
+// If tabSize <= 0, ExpandTabs panics with error.
+//
+// Samples:
+//     ExpandTabs("a\tbc\tdef\tghij\tk", 4) => "a   bc  def ghij    k"
+//     ExpandTabs("abcdefg\thij\nk\tl", 4)  => "abcdefg hij\nk   l"
+//     ExpandTabs("z中\t文\tw", 4)           => "z中 文  w"
+func ExpandTabs(str string, tabSize int) string {
+	if tabSize <= 0 {
+		panic("tab size must be positive")
+	}
+
+	var r rune
+	var i, size, column, expand int
+	var output *bytes.Buffer
+
+	orig := str
+
+	for len(str) > 0 {
+		r, size = utf8.DecodeRuneInString(str)
+
+		if r == '\t' {
+			expand = tabSize - column%tabSize
+
+			if output == nil {
+				output = allocBuffer(orig, str)
+			}
+
+			for i = 0; i < expand; i++ {
+				output.WriteByte(byte(' '))
+			}
+
+			column += expand
+		} else {
+			if r == '\n' {
+				column = 0
+			} else {
+				column += RuneWidth(r)
+			}
+
+			if output != nil {
+				output.WriteRune(r)
+			}
+		}
+
+		str = str[size:]
+	}
+
+	if output == nil {
+		return orig
+	}
+
+	return output.String()
+}
+
+// LeftJustify returns a string with pad string at right side if str's rune length is smaller than length.
+// If str's rune length is larger than length, str itself will be returned.
+//
+// If pad is an empty string, str will be returned.
+//
+// Samples:
+//     LeftJustify("hello", 4, " ")    => "hello"
+//     LeftJustify("hello", 10, " ")   => "hello     "
+//     LeftJustify("hello", 10, "123") => "hello12312"
+func LeftJustify(str string, length int, pad string) string {
+	l := Len(str)
+
+	if l >= length || pad == "" {
+		return str
+	}
+
+	remains := length - l
+	padLen := Len(pad)
+
+	output := &bytes.Buffer{}
+	output.Grow(len(str) + (remains/padLen+1)*len(pad))
+	output.WriteString(str)
+	writePadString(output, pad, padLen, remains)
+	return output.String()
+}
+
+// RightJustify returns a string with pad string at left side if str's rune length is smaller than length.
+// If str's rune length is larger than length, str itself will be returned.
+//
+// If pad is an empty string, str will be returned.
+//
+// Samples:
+//     RightJustify("hello", 4, " ")    => "hello"
+//     RightJustify("hello", 10, " ")   => "     hello"
+//     RightJustify("hello", 10, "123") => "12312hello"
+func RightJustify(str string, length int, pad string) string {
+	l := Len(str)
+
+	if l >= length || pad == "" {
+		return str
+	}
+
+	remains := length - l
+	padLen := Len(pad)
+
+	output := &bytes.Buffer{}
+	output.Grow(len(str) + (remains/padLen+1)*len(pad))
+	writePadString(output, pad, padLen, remains)
+	output.WriteString(str)
+	return output.String()
+}
+
+// Center returns a string with pad string at both side if str's rune length is smaller than length.
+// If str's rune length is larger than length, str itself will be returned.
+//
+// If pad is an empty string, str will be returned.
+//
+// Samples:
+//     Center("hello", 4, " ")    => "hello"
+//     Center("hello", 10, " ")   => "  hello   "
+//     Center("hello", 10, "123") => "12hello123"
+func Center(str string, length int, pad string) string {
+	l := Len(str)
+
+	if l >= length || pad == "" {
+		return str
+	}
+
+	remains := length - l
+	padLen := Len(pad)
+
+	output := &bytes.Buffer{}
+	output.Grow(len(str) + (remains/padLen+1)*len(pad))
+	writePadString(output, pad, padLen, remains/2)
+	output.WriteString(str)
+	writePadString(output, pad, padLen, (remains+1)/2)
+	return output.String()
+}
+
+func writePadString(output *bytes.Buffer, pad string, padLen, remains int) {
+	var r rune
+	var size int
+
+	repeats := remains / padLen
+
+	for i := 0; i < repeats; i++ {
+		output.WriteString(pad)
+	}
+
+	remains = remains % padLen
+
+	if remains != 0 {
+		for i := 0; i < remains; i++ {
+			r, size = utf8.DecodeRuneInString(pad)
+			output.WriteRune(r)
+			pad = pad[size:]
+		}
+	}
+}