Add Update Package Versions Known By asdf Plugin as a unix til

README.md

@@ -10,7 +10,7 @@ pairing with smart people at Hashrocket.
 
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-_991 TILs and counting..._
+_992 TILs and counting..._
 
 ---
 
@@ -975,6 +975,7 @@ _991 TILs and counting..._
 - [Switch Versions of a Brew Formula](unix/switch-versions-of-a-brew-formula.md)
 - [Touch Access And Modify Times Individually](unix/touch-access-and-modify-times-individually.md)
 - [Undo Some Command Line Editing](unix/undo-some-command-line-editing.md)
+- [Update Package Versions Known By asdf Plugin](unix/update-package-versions-known-by-asdf-plugin.md)
 - [Use Regex Pattern Matching With Grep](unix/use-regex-pattern-matching-with-grep.md)
 - [View A Web Page In The Terminal](unix/view-a-web-page-in-the-terminal.md)
 - [Watch The Difference](unix/watch-the-difference.md)

unix/update-package-versions-known-by-asdf-plugin.md

@@ -0,0 +1,15 @@
+# Update Package Versions Known By asdf Plugin
+
+When you run `asdf list-all ruby`, asdf will list all the package versions it
+knows about for that plugin. This list is based on when the plugin was most
+recently installed or updated. If it has been a while, there are likely new
+versions that asdf doesn't know about.
+
+This list can be updated with the `update-plugin` command:
+
+```bash
+$ asdf update-plugin ruby
+```
+
+Now, the next time you run `asdf list-all ruby`, you'll have an up-to-date
+listing of available package versions.