Thanks. Your post spurred me to dig into the kookma library to understand the flow.
TW checks the plugin library index file, which in Kookma’s case is
https://kookma.github.io/TW-PluginLibrary/library/index.html
It has an entry like this for every plugin.
{
"title": "$:/plugins/kookma/commander",
"description": "batch processing tiddlers",
"name": "Tiddler Commander",
"author": "Mohammad Rahmani",
"version": "2.1.3",
"core-version": ">=5.1.22",
"source": "https://github.com/kookma/TW-Commander",
"list": "readme history license authors",
"dependents": "",
"plugin-type": "plugin",
"type": "application/json",
"readme": "; Tiddler Commander\nTiddler Commander, in short ''Commander'' is a unique tool for batch operations on tiddlers. Commander has the below features\n\n* Bulk tiddler creation/deletion\n* Combo search to filter and select tiddlers\n* Title operation: add, remove prefixes and suffixes, also remove cahras form begining and end of title (on renaming tiddlers, [[relink|$:/plugins/kookma/commander/help/uicomp/relink]] can be used to update title in other tiddlers)\n* Tag operation: add, remove, replace\n* Field operation: add, remove, rename, and set field value\n* SNR, search and replace in all fields including text, tags, //title//, and common fields\n* Inspect, to review and inspect tiddlers in one place, scroll among them and edit all fields (including common fields), tags, text (title is an exception!)\n* Log, create logs of all operations\n* Search, //save and load// any combination of filter search\n\n; Start Commander\n* Normally Commander adds its icon: <span class=\"cmd-doc\">{{$:/plugins/kookma/commander/images/commander.svg}}</span> to page controls.\n* Open the right sidebar and click on the <span class=\"cmd-doc\">{{$:/plugins/kookma/commander/images/commander.svg}}</span> Commander is started\n* In standard Tiddlywiki, control buttons are shown on the right sidebar under site title.\n\n; Code and demo\nFor learning plugin features, syntax, tutorial and examples see the plugin demo and code pages\n\n* Demo: https://kookma.github.io/TW-Commander/\n* Code: https://github.com/kookma/TW-Commander\n\n<style>\n.cmd-doc svg{\nwidth: 1.2em;\nheight: 1.2em;\nvertical-align: middle;}\n</style>",
"requires-reload": "yes"
}
If the version
field has a newer entry than the present in TW, then TW shows an update available message.
If the library maintainer is not diligent in updating the version field, you will never know about the update.
Still, it is better than nothing.
Though, looking into the GitHub repository for release tags might be better.