pkg/dockerscript: expose a simple, clean API with a single Parse method

Docker-DCO-1.1-Signed-off-by: Solomon Hykes <solomon@docker.com> (github: shykes)

dockerscript/scanner/extra.go

@@ -0,0 +1,22 @@
+package scanner
+
+import (
+	"unicode"
+	"strings"
+)
+
+// extra functions used to hijack the upstream text/scanner
+
+func detectIdent(ch rune) bool {
+	if unicode.IsLetter(ch) {
+		return true
+	}
+	if unicode.IsDigit(ch) {
+		return true
+	}
+	if strings.ContainsRune("_:/+-@%^", ch) {
+		return true
+	}
+	return false
+}
+