Introduce "thisTiddler" variable (#7182)

* Initial Commit

* Change of mind: Do not blank thisTiddler within macros

* Revert previous implementation

* Somewhat simpler implementation

* Add docs

* Add docs version tag

core/modules/widgets/transclude.js

@@ -279,6 +279,8 @@ TranscludeWidget.prototype.getTransclusionTarget = function() {
 							defaultType: this.transcludeType
 						});
 	}
+	// Set 'thisTiddler'
+	this.setVariable("thisTiddler",this.transcludeTitle);
 	// Return the parse tree
 	if(parser) {
 		return {

editions/test/tiddlers/tests/data/this-tiddler/Simple.tid

@@ -0,0 +1,29 @@
+title: ThisTiddler/Simple
+description: Simple usage of thisTiddler variable
+type: text/vnd.tiddlywiki-multiple
+tags: [[$:/tags/wiki-test-spec]]
+
+title: Output
+
+\whitespace trim
+\import Macro
+\define print-this-tiddler()
+<$text text=<<thisTiddler>>/>
+\end
+
+(<$text text=<<thisTiddler>>/>)
+
+(<<print-this-tiddler>>)
+
+(<<imported-print-this-tiddler>>)
+
++
+title: Macro
+
+\define imported-print-this-tiddler()
+<$text text=<<thisTiddler>>/>
+\end
++
+title: ExpectedResult
+
+<p>(Output)</p><p>(Output)</p><p>(Output)</p>

editions/tw5.com/tiddlers/system/doc-macros.tid

@@ -134,7 +134,11 @@ This is an example tiddler. See [[Table-of-Contents Macros (Examples)]].
 	</dl>
 	<blockquote class="doc-example-result">
 	<$reveal default="$egvar$" type="match" text="NO-SUCH-VAR">
-		$eg$
+
+$$$text/vnd.tiddlywiki
+$eg$
+$$$
+
 	</$reveal>
 	<$reveal default="$egvar$" type="nomatch" text="NO-SUCH-VAR">
 		<<$egvar$>>

editions/tw5.com/tiddlers/thisTiddler Variable (Examples).tid

@@ -0,0 +1,13 @@
+created: 20230304123606350
+modified: 20230304124149055
+tags: [[currentTiddler Variable]] [[Variable Examples]]
+title: thisTiddler Variable (Examples)
+type: text/vnd.tiddlywiki
+
+
+
+<$macrocall $name=".example" n="1" eg="""<$text text=<<thisTiddler>>/>"""/>
+
+<$macrocall $name=".example" n="2" eg="""\define example() <$text text=<<thisTiddler>>/>
+<<example>>
+"""/>

editions/tw5.com/tiddlers/thisTiddler Variable.tid

@@ -0,0 +1,12 @@
+caption: currentTiddler
+created: 20230304122810114
+modified: 20230304123557862
+tags: Variables [[Core Variables]]
+title: thisTiddler Variable
+type: text/vnd.tiddlywiki
+
+<<.from-version "5.3.0">> The <<.def thisTiddler>> [[variable|Variables]] is set by the <<.wlink TranscludeWidget>> widget to contain the title of the tiddler that was transcluded. This means that within a tiddler <<.def thisTiddler>> will contain the title of that tiddler. It is not affected by macros, which means that within a macro <<.def thisTiddler>> will contain the title of the tiddler from which the macro was invoked. Intermediate, nested macro calls are ignored.
+
+Compare <<.vlink storyTiddler>> and <<.vlink currentTiddler>>.
+
+<<.variable-examples "thisTiddler">>