Create setting for default type of draft tiddlers (#8783)

* Proof of concept to change type of tiddlers created by editing missing.

* Adding a setting for default type so that it can be overridden for other wikis.

* Incorporating PR feedback.

* Adding documentation tiddler for new setting.

* Added documentation to the markdown plugin documentation.

* Added documentation to the markdown plugin documentation.

* Added notice to markdown edition.

core/modules/widgets/navigator.js

@@ -277,6 +277,8 @@ NavigatorWidget.prototype.makeDraftTiddler = function(targetTitle) {
 	}
 	// Get the current value of the tiddler we're editing
 	var tiddler = this.wiki.getTiddler(targetTitle);
+	var defaultType = this.wiki.getTiddlerText("$:/config/DefaultMissingType", "").trim();
+	var defaultFields = { type: defaultType };
 	// Save the initial value of the draft tiddler
 	draftTitle = this.generateDraftTitle(targetTitle);
 	var draftTiddler = new $tw.Tiddler({
@@ -288,7 +290,8 @@ NavigatorWidget.prototype.makeDraftTiddler = function(targetTitle) {
 				"draft.title": targetTitle,
 				"draft.of": targetTitle
 			},
-			this.wiki.getModificationFields()
+			this.wiki.getModificationFields(),
+			tiddler === null || tiddler === undefined ? defaultFields : {}
 		);
 	this.wiki.addTiddler(draftTiddler);
 	return draftTiddler;

editions/markdowndemo/tiddlers/DefaultMissingType.tid

@@ -0,0 +1,3 @@
+title: $:/config/DefaultMissingType
+
+text/markdown

editions/markdowndemo/tiddlers/HelloThere.tid

@@ -7,3 +7,9 @@ This is a demo of TiddlyWiki5 incorporating a plugin for parsing tiddlers writte
 To add the plugin to your own TiddlyWiki5, just drag this link to the browser window:
 
 [[$:/plugins/tiddlywiki/markdown]]
+
+! Overridden Defaults
+
+This demo overrides the default value for tiddlers created from missing tiddler
+links so that Markdown is the default rather than WikiText. See
+the [[$:/config/DefaultMissingType]] tiddler for the modification.

editions/tw5.com/tiddlers/hiddensettings/Hidden Setting DefaultMissingType.tid

@@ -0,0 +1,7 @@
+tags: [[Hidden Settings]]
+title: Hidden Setting: Default-Missing Type
+type: text/vnd.tiddlywiki
+
+By default new tiddlers are created with a blank content type.
+
+The hidden setting in $:/config/DefaultMissingType can be set to another content type which is used by default for new tiddlers created by clicking on a missing link (for example, `text/markdown` to default to Markdown for missing tiddlers). If no value is provided, the content type will be blank and WikiText will be used.

plugins/tiddlywiki/markdown/readme.tid

@@ -99,3 +99,21 @@ When [[typographer|$:/config/markdown/typographer]] is enabled, markdown-it will
 --        → –
 ---       → —
 ```
+
+! Making Markdown the Default in TiddlyWiki
+
+!! Modifying Existing Actions
+
+Adding `type="text/markdown"` to the actions of the following buttons will
+override the default behavior.
+
+* New Journal - $:/core/ui/Actions/new-journal
+* New Tiddler Here - $:/core/ui/Buttons/new-here
+* New Tiddler - $:/core/ui/Actions/new-tiddler
+
+!! Using Markdown for Missing Links
+
+By default, missing tiddlers are created with a blank content type, which
+implies WikiText. Setting [[$:/config/DefaultMissingType]] to `text/markdown`
+will make it so that tiddlers created from a missing tiddler link will be in
+Markdown rather than in WikiText.