Add dedent pkg

vendor/github.com/renstrom/dedent/dedent.go

@@ -0,0 +1,49 @@
+package dedent
+
+import (
+	"regexp"
+	"strings"
+)
+
+var (
+	whitespaceOnly    = regexp.MustCompile("(?m)^[ \t]+$")
+	leadingWhitespace = regexp.MustCompile("(?m)(^[ \t]*)(?:[^ \t\n])")
+)
+
+// Dedent removes any common leading whitespace from every line in text.
+//
+// This can be used to make multiline strings to line up with the left edge of
+// the display, while still presenting them in the source code in indented
+// form.
+func Dedent(text string) string {
+	var margin string
+
+	text = whitespaceOnly.ReplaceAllString(text, "")
+	indents := leadingWhitespace.FindAllStringSubmatch(text, -1)
+
+	// Look for the longest leading string of spaces and tabs common to all
+	// lines.
+	for i, indent := range indents {
+		if i == 0 {
+			margin = indent[1]
+		} else if strings.HasPrefix(indent[1], margin) {
+			// Current line more deeply indented than previous winner:
+			// no change (previous winner is still on top).
+			continue
+		} else if strings.HasPrefix(margin, indent[1]) {
+			// Current line consistent with and no deeper than previous winner:
+			// it's the new winner.
+			margin = indent[1]
+		} else {
+			// Current line and previous winner have no common whitespace:
+			// there is no margin.
+			margin = ""
+			break
+		}
+	}
+
+	if margin != "" {
+		text = regexp.MustCompile("(?m)^"+margin).ReplaceAllString(text, "")
+	}
+	return text
+}