FEAT: added supplement mezzanine function which appends a value into a block if not yet present

resolves: Oldes/Rebol-wishes#11

Author: Oldes

src/mezz/mezz-series.reb

@@ -380,6 +380,23 @@ alter: func [
 	) [append series :value]
 ]
 
+supplement: func [
+	"Append value if not found; returns series at same position."
+	series [block!] {(modified)}
+	value
+	/case "Case-sensitive comparison"
+	/local result
+][
+	result: series ; to return series at same position if value is found
+	any[
+		either case [
+			find/case series :value
+		][  find      series :value ]
+		append series :value
+	]
+	result
+]
+
 collect: func [
 	"Evaluates a block, storing values via KEEP function, and returns block of collected values."
 	body [block!] "Block to evaluate"

src/tests/units/module-test.r3

@@ -3,15 +3,15 @@ Rebol [
 	Author:  "Peter W A Wood, Oldes"
 	File: 	 %module-test.r3
 	Tabs:	 4
-	Needs:   [%../quick-test-module.r3]
+	Needs:   %../quick-test-module.r3
 ]
 
 ~~~start-file~~~ "module!"
 
-modules-test-dir: join what-dir %units/files/
-unless find system/options/module-paths modules-test-dir [
-	append system/options/module-paths modules-test-dir
-]
+; extend module-paths with units/files/ directory
+; so modules there can be located
+supplement system/options/module-paths join what-dir %units/files/
+
 
 ===start-group=== "module keywords"
 	--test-- "hidden"

src/tests/units/series-test.r3

@@ -169,6 +169,16 @@ Rebol [
 	--assert #"b" = select/same "aAbcdAe" "A"
 	--assert #"e" = select/same/last "aAbcdAe" "A"
 
+--test- "SUPPLEMENT"
+	;@@ https://github.com/Oldes/Rebol-wishes/issues/11
+	b: []
+	--assert [%a]         = supplement b %a
+	--assert [%a %b]      = supplement b %b
+	--assert [%a %b]      = supplement b %a
+	--assert [%a %b #"a"] = supplement b #"a"
+	--assert [%a %b #"a"] = supplement b #"A" ; case-insensitive
+	--assert [%a %b #"a" #"A"] = supplement/case b #"A"
+
 ===end-group===
 
 ===start-group=== "PATH notation"