FEAT: including R2's version of the build-tag function

(but not enabled by default in boot-files)

Related to: Oldes/Rebol-issues#370

src/mezz/boot-files.r

@@ -49,6 +49,7 @@ REBOL [
 	%mezz-colors.r
 	%mezz-crypt.r
 	%mezz-date.r ; Internet date support
+	;%mezz-tag.r  ; build-tag
 	%mezz-tail.r
 	%codec-json.r
 	%codec-unixtime.r

src/mezz/mezz-tag.r

@@ -0,0 +1,41 @@
+REBOL [
+	System: "REBOL [R3] Language Interpreter and Run-time Environment"
+	Title: "REBOL 3 Mezzanine: Tag"
+	Rights: {
+		Copyright 2012 REBOL Technologies
+		REBOL is a trademark of REBOL Technologies
+	}
+	License: {
+		Licensed under the Apache License, Version 2.0
+		See: http://www.apache.org/licenses/LICENSE-2.0
+	}
+]
+
+build-tag: func [
+    "Generates a tag from a composed block."
+    values [block!] "Block of parens to evaluate and other data."
+    /local tag value-rule xml? name attribute value
+][  ;@@ slightly modified version from Rebol2
+    tag: make string! 7 * length? values
+    value-rule: [
+        set value issue! (value: mold value)
+        | set value file! (value: replace/all copy value #" " "%20")
+        | set value any-type! (value: replace/all form value #"'" {\'})
+    ]
+    xml?: false
+    parse compose values [
+        [
+            set name ['?xml (xml?: true) | word! | url!] (append tag name)
+            any [
+                set attribute [word! | url!] value-rule (
+                    append tag ajoin [#" " attribute {='} value #"'"]
+                )
+                | value-rule (append tag join #" " value)
+            ]
+            end (if xml? [append tag #"?"])
+        ]
+        |
+        [set name refinement! to end (tag: mold name)]
+    ]
+    to tag! tag
+]